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introduction mitosis is used for almost all of your body ’ s cell division needs . it adds new cells during development and replaces old and worn-out cells throughout your life . the goal of mitosis is to produce daughter cells that are genetically identical to their mothers , with not a single chromosome more or less . meiosis , on the other hand , is used for just one purpose in the human body : the production of gametes—sex cells , or sperm and eggs . its goal is to make daughter cells with exactly half as many chromosomes as the starting cell . to put that another way , meiosis in humans is a division process that takes us from a diploid cell—one with two sets of chromosomes—to haploid cells—ones with a single set of chromosomes . in humans , the haploid cells made in meiosis are sperm and eggs . when a sperm and an egg join in fertilization , the two haploid sets of chromosomes form a complete diploid set : a new genome . phases of meiosis in many ways , meiosis is a lot like mitosis . the cell goes through similar stages and uses similar strategies to organize and separate chromosomes . in meiosis , however , the cell has a more complex task . it still needs to separate sister chromatids ( the two halves of a duplicated chromosome ) , as in mitosis . but it must also separate homologous chromosomes , the similar but nonidentical chromosome pairs an organism receives from its two parents . these goals are accomplished in meiosis using a two-step division process . homologue pairs separate during a first round of cell division , called meiosis i . sister chromatids separate during a second round , called meiosis ii . since cell division occurs twice during meiosis , one starting cell can produce four gametes ( eggs or sperm ) . in each round of division , cells go through four stages : prophase , metaphase , anaphase , and telophase . meiosis i before entering meiosis i , a cell must first go through interphase . as in mitosis , the cell grows during g $ _1 $ phase , copies all of its chromosomes during s phase , and prepares for division during g $ _2 $ phase . during prophase i , differences from mitosis begin to appear . as in mitosis , the chromosomes begin to condense , but in meiosis i , they also pair up . each chromosome carefully aligns with its homologue partner so that the two match up at corresponding positions along their full length . for instance , in the image below , the letters a , b , and c represent genes found at particular spots on the chromosome , with capital and lowercase letters for different forms , or alleles , of each gene . the dna is broken at the same spot on each homologue—here , between genes b and c—and reconnected in a criss-cross pattern so that the homologues exchange part of their dna . this process , in which homologous chromosomes trade parts , is called crossing over . it 's helped along by a protein structure called the synaptonemal complex that holds the homologues together . the chromosomes would actually be positioned one on top of the other—as in the image below—throughout crossing over ; they 're only shown side-by-side in the image above so that it 's easier to see the exchange of genetic material . you can see crossovers under a microscope as chiasmata , cross-shaped structures where homologues are linked together . chiasmata keep the homologues connected to each other after the synaptonemal complex breaks down , so each homologous pair needs at least one . it 's common for multiple crossovers ( up to $ 25 $ ! ) to take place for each homologue pair $ ^1 $ . the spots where crossovers happen are more or less random , leading to the formation of new , `` remixed '' chromosomes with unique combinations of alleles . after crossing over , the spindle begins to capture chromosomes and move them towards the center of the cell ( metaphase plate ) . this may seem familiar from mitosis , but there is a twist . each chromosome attaches to microtubules from just one pole of the spindle , and the two homologues of a pair bind to microtubules from opposite poles . so , during metaphase i , homologue pairs—not individual chromosomes—line up at the metaphase plate for separation . when the homologous pairs line up at the metaphase plate , the orientation of each pair is random . for instance , in the diagram above , the pink version of the big chromosome and the purple version of the little chromosome happen to be positioned towards the same pole and go into the same cell . but the orientation could have equally well been flipped , so that both purple chromosomes went into the cell together . this allows for the formation of gametes with different sets of homologues . in anaphase i , the homologues are pulled apart and move apart to opposite ends of the cell . the sister chromatids of each chromosome , however , remain attached to one another and do n't come apart . finally , in telophase i , the chromosomes arrive at opposite poles of the cell . in some organisms , the nuclear membrane re-forms and the chromosomes decondense , although in others , this step is skipped—since cells will soon go through another round of division , meiosis ii $ ^ { 2,3 } $ . cytokinesis usually occurs at the same time as telophase i , forming two haploid daughter cells . meiosis ii cells move from meiosis i to meiosis ii without copying their dna . meiosis ii is a shorter and simpler process than meiosis i , and you may find it helpful to think of meiosis ii as “ mitosis for haploid cells . '' the cells that enter meiosis ii are the ones made in meiosis i . these cells are haploid—have just one chromosome from each homologue pair—but their chromosomes still consist of two sister chromatids . in meiosis ii , the sister chromatids separate , making haploid cells with non-duplicated chromosomes . during prophase ii , chromosomes condense and the nuclear envelope breaks down , if needed . the centrosomes move apart , the spindle forms between them , and the spindle microtubules begin to capture chromosomes . the two sister chromatids of each chromosome are captured by microtubules from opposite spindle poles . in metaphase ii , the chromosomes line up individually along the metaphase plate . in anaphase ii , the sister chromatids separate and are pulled towards opposite poles of the cell . in telophase ii , nuclear membranes form around each set of chromosomes , and the chromosomes decondense . cytokinesis splits the chromosome sets into new cells , forming the final products of meiosis : four haploid cells in which each chromosome has just one chromatid . in humans , the products of meiosis are sperm or egg cells . how meiosis `` mixes and matches '' genes the gametes produced in meiosis are all haploid , but they 're not genetically identical . for example , take a look the meiosis ii diagram above , which shows the products of meiosis for a cell with $ 2n = 4 $ chromosomes . each gamete has a unique `` sample '' of the genetic material present in the starting cell . as it turns out , there are many more potential gamete types than just the four shown in the diagram , even for a cell with with only four chromosomes . the two main reason we can get many genetically different gametes are : crossing over . the points where homologues cross over and exchange genetic material are chosen more or less at random , and they will be different in each cell that goes through meiosis . if meiosis happens many times , as in humans , crossovers will happen at many different points . random orientation of homologue pairs . the random orientation of homologue pairs in metaphase i allows for the production of gametes with many different assortments of homologous chromosomes . in a human cell , the random orientation of homologue pairs alone allows for over $ 8 $ $ \text { million } $ different types of possible gametes $ ^7 $ . when we layer crossing over on top of this , the number of genetically different gametes that you—or any other person—can make is effectively infinite . check out the video on variation in a species to learn how genetic diversity generated by meiosis ( and fertilization ) is important in evolution and helps populations survive .
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in some organisms , the nuclear membrane re-forms and the chromosomes decondense , although in others , this step is skipped—since cells will soon go through another round of division , meiosis ii $ ^ { 2,3 } $ . cytokinesis usually occurs at the same time as telophase i , forming two haploid daughter cells . meiosis ii cells move from meiosis i to meiosis ii without copying their dna .
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then how does a haploid cell produce two more haploid cells without going through dna replication ?
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introduction mitosis is used for almost all of your body ’ s cell division needs . it adds new cells during development and replaces old and worn-out cells throughout your life . the goal of mitosis is to produce daughter cells that are genetically identical to their mothers , with not a single chromosome more or less . meiosis , on the other hand , is used for just one purpose in the human body : the production of gametes—sex cells , or sperm and eggs . its goal is to make daughter cells with exactly half as many chromosomes as the starting cell . to put that another way , meiosis in humans is a division process that takes us from a diploid cell—one with two sets of chromosomes—to haploid cells—ones with a single set of chromosomes . in humans , the haploid cells made in meiosis are sperm and eggs . when a sperm and an egg join in fertilization , the two haploid sets of chromosomes form a complete diploid set : a new genome . phases of meiosis in many ways , meiosis is a lot like mitosis . the cell goes through similar stages and uses similar strategies to organize and separate chromosomes . in meiosis , however , the cell has a more complex task . it still needs to separate sister chromatids ( the two halves of a duplicated chromosome ) , as in mitosis . but it must also separate homologous chromosomes , the similar but nonidentical chromosome pairs an organism receives from its two parents . these goals are accomplished in meiosis using a two-step division process . homologue pairs separate during a first round of cell division , called meiosis i . sister chromatids separate during a second round , called meiosis ii . since cell division occurs twice during meiosis , one starting cell can produce four gametes ( eggs or sperm ) . in each round of division , cells go through four stages : prophase , metaphase , anaphase , and telophase . meiosis i before entering meiosis i , a cell must first go through interphase . as in mitosis , the cell grows during g $ _1 $ phase , copies all of its chromosomes during s phase , and prepares for division during g $ _2 $ phase . during prophase i , differences from mitosis begin to appear . as in mitosis , the chromosomes begin to condense , but in meiosis i , they also pair up . each chromosome carefully aligns with its homologue partner so that the two match up at corresponding positions along their full length . for instance , in the image below , the letters a , b , and c represent genes found at particular spots on the chromosome , with capital and lowercase letters for different forms , or alleles , of each gene . the dna is broken at the same spot on each homologue—here , between genes b and c—and reconnected in a criss-cross pattern so that the homologues exchange part of their dna . this process , in which homologous chromosomes trade parts , is called crossing over . it 's helped along by a protein structure called the synaptonemal complex that holds the homologues together . the chromosomes would actually be positioned one on top of the other—as in the image below—throughout crossing over ; they 're only shown side-by-side in the image above so that it 's easier to see the exchange of genetic material . you can see crossovers under a microscope as chiasmata , cross-shaped structures where homologues are linked together . chiasmata keep the homologues connected to each other after the synaptonemal complex breaks down , so each homologous pair needs at least one . it 's common for multiple crossovers ( up to $ 25 $ ! ) to take place for each homologue pair $ ^1 $ . the spots where crossovers happen are more or less random , leading to the formation of new , `` remixed '' chromosomes with unique combinations of alleles . after crossing over , the spindle begins to capture chromosomes and move them towards the center of the cell ( metaphase plate ) . this may seem familiar from mitosis , but there is a twist . each chromosome attaches to microtubules from just one pole of the spindle , and the two homologues of a pair bind to microtubules from opposite poles . so , during metaphase i , homologue pairs—not individual chromosomes—line up at the metaphase plate for separation . when the homologous pairs line up at the metaphase plate , the orientation of each pair is random . for instance , in the diagram above , the pink version of the big chromosome and the purple version of the little chromosome happen to be positioned towards the same pole and go into the same cell . but the orientation could have equally well been flipped , so that both purple chromosomes went into the cell together . this allows for the formation of gametes with different sets of homologues . in anaphase i , the homologues are pulled apart and move apart to opposite ends of the cell . the sister chromatids of each chromosome , however , remain attached to one another and do n't come apart . finally , in telophase i , the chromosomes arrive at opposite poles of the cell . in some organisms , the nuclear membrane re-forms and the chromosomes decondense , although in others , this step is skipped—since cells will soon go through another round of division , meiosis ii $ ^ { 2,3 } $ . cytokinesis usually occurs at the same time as telophase i , forming two haploid daughter cells . meiosis ii cells move from meiosis i to meiosis ii without copying their dna . meiosis ii is a shorter and simpler process than meiosis i , and you may find it helpful to think of meiosis ii as “ mitosis for haploid cells . '' the cells that enter meiosis ii are the ones made in meiosis i . these cells are haploid—have just one chromosome from each homologue pair—but their chromosomes still consist of two sister chromatids . in meiosis ii , the sister chromatids separate , making haploid cells with non-duplicated chromosomes . during prophase ii , chromosomes condense and the nuclear envelope breaks down , if needed . the centrosomes move apart , the spindle forms between them , and the spindle microtubules begin to capture chromosomes . the two sister chromatids of each chromosome are captured by microtubules from opposite spindle poles . in metaphase ii , the chromosomes line up individually along the metaphase plate . in anaphase ii , the sister chromatids separate and are pulled towards opposite poles of the cell . in telophase ii , nuclear membranes form around each set of chromosomes , and the chromosomes decondense . cytokinesis splits the chromosome sets into new cells , forming the final products of meiosis : four haploid cells in which each chromosome has just one chromatid . in humans , the products of meiosis are sperm or egg cells . how meiosis `` mixes and matches '' genes the gametes produced in meiosis are all haploid , but they 're not genetically identical . for example , take a look the meiosis ii diagram above , which shows the products of meiosis for a cell with $ 2n = 4 $ chromosomes . each gamete has a unique `` sample '' of the genetic material present in the starting cell . as it turns out , there are many more potential gamete types than just the four shown in the diagram , even for a cell with with only four chromosomes . the two main reason we can get many genetically different gametes are : crossing over . the points where homologues cross over and exchange genetic material are chosen more or less at random , and they will be different in each cell that goes through meiosis . if meiosis happens many times , as in humans , crossovers will happen at many different points . random orientation of homologue pairs . the random orientation of homologue pairs in metaphase i allows for the production of gametes with many different assortments of homologous chromosomes . in a human cell , the random orientation of homologue pairs alone allows for over $ 8 $ $ \text { million } $ different types of possible gametes $ ^7 $ . when we layer crossing over on top of this , the number of genetically different gametes that you—or any other person—can make is effectively infinite . check out the video on variation in a species to learn how genetic diversity generated by meiosis ( and fertilization ) is important in evolution and helps populations survive .
|
cytokinesis usually occurs at the same time as telophase i , forming two haploid daughter cells . meiosis ii cells move from meiosis i to meiosis ii without copying their dna . meiosis ii is a shorter and simpler process than meiosis i , and you may find it helpful to think of meiosis ii as “ mitosis for haploid cells . ''
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is reduction of chromosomal number is only advantage of meiosis ?
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introduction mitosis is used for almost all of your body ’ s cell division needs . it adds new cells during development and replaces old and worn-out cells throughout your life . the goal of mitosis is to produce daughter cells that are genetically identical to their mothers , with not a single chromosome more or less . meiosis , on the other hand , is used for just one purpose in the human body : the production of gametes—sex cells , or sperm and eggs . its goal is to make daughter cells with exactly half as many chromosomes as the starting cell . to put that another way , meiosis in humans is a division process that takes us from a diploid cell—one with two sets of chromosomes—to haploid cells—ones with a single set of chromosomes . in humans , the haploid cells made in meiosis are sperm and eggs . when a sperm and an egg join in fertilization , the two haploid sets of chromosomes form a complete diploid set : a new genome . phases of meiosis in many ways , meiosis is a lot like mitosis . the cell goes through similar stages and uses similar strategies to organize and separate chromosomes . in meiosis , however , the cell has a more complex task . it still needs to separate sister chromatids ( the two halves of a duplicated chromosome ) , as in mitosis . but it must also separate homologous chromosomes , the similar but nonidentical chromosome pairs an organism receives from its two parents . these goals are accomplished in meiosis using a two-step division process . homologue pairs separate during a first round of cell division , called meiosis i . sister chromatids separate during a second round , called meiosis ii . since cell division occurs twice during meiosis , one starting cell can produce four gametes ( eggs or sperm ) . in each round of division , cells go through four stages : prophase , metaphase , anaphase , and telophase . meiosis i before entering meiosis i , a cell must first go through interphase . as in mitosis , the cell grows during g $ _1 $ phase , copies all of its chromosomes during s phase , and prepares for division during g $ _2 $ phase . during prophase i , differences from mitosis begin to appear . as in mitosis , the chromosomes begin to condense , but in meiosis i , they also pair up . each chromosome carefully aligns with its homologue partner so that the two match up at corresponding positions along their full length . for instance , in the image below , the letters a , b , and c represent genes found at particular spots on the chromosome , with capital and lowercase letters for different forms , or alleles , of each gene . the dna is broken at the same spot on each homologue—here , between genes b and c—and reconnected in a criss-cross pattern so that the homologues exchange part of their dna . this process , in which homologous chromosomes trade parts , is called crossing over . it 's helped along by a protein structure called the synaptonemal complex that holds the homologues together . the chromosomes would actually be positioned one on top of the other—as in the image below—throughout crossing over ; they 're only shown side-by-side in the image above so that it 's easier to see the exchange of genetic material . you can see crossovers under a microscope as chiasmata , cross-shaped structures where homologues are linked together . chiasmata keep the homologues connected to each other after the synaptonemal complex breaks down , so each homologous pair needs at least one . it 's common for multiple crossovers ( up to $ 25 $ ! ) to take place for each homologue pair $ ^1 $ . the spots where crossovers happen are more or less random , leading to the formation of new , `` remixed '' chromosomes with unique combinations of alleles . after crossing over , the spindle begins to capture chromosomes and move them towards the center of the cell ( metaphase plate ) . this may seem familiar from mitosis , but there is a twist . each chromosome attaches to microtubules from just one pole of the spindle , and the two homologues of a pair bind to microtubules from opposite poles . so , during metaphase i , homologue pairs—not individual chromosomes—line up at the metaphase plate for separation . when the homologous pairs line up at the metaphase plate , the orientation of each pair is random . for instance , in the diagram above , the pink version of the big chromosome and the purple version of the little chromosome happen to be positioned towards the same pole and go into the same cell . but the orientation could have equally well been flipped , so that both purple chromosomes went into the cell together . this allows for the formation of gametes with different sets of homologues . in anaphase i , the homologues are pulled apart and move apart to opposite ends of the cell . the sister chromatids of each chromosome , however , remain attached to one another and do n't come apart . finally , in telophase i , the chromosomes arrive at opposite poles of the cell . in some organisms , the nuclear membrane re-forms and the chromosomes decondense , although in others , this step is skipped—since cells will soon go through another round of division , meiosis ii $ ^ { 2,3 } $ . cytokinesis usually occurs at the same time as telophase i , forming two haploid daughter cells . meiosis ii cells move from meiosis i to meiosis ii without copying their dna . meiosis ii is a shorter and simpler process than meiosis i , and you may find it helpful to think of meiosis ii as “ mitosis for haploid cells . '' the cells that enter meiosis ii are the ones made in meiosis i . these cells are haploid—have just one chromosome from each homologue pair—but their chromosomes still consist of two sister chromatids . in meiosis ii , the sister chromatids separate , making haploid cells with non-duplicated chromosomes . during prophase ii , chromosomes condense and the nuclear envelope breaks down , if needed . the centrosomes move apart , the spindle forms between them , and the spindle microtubules begin to capture chromosomes . the two sister chromatids of each chromosome are captured by microtubules from opposite spindle poles . in metaphase ii , the chromosomes line up individually along the metaphase plate . in anaphase ii , the sister chromatids separate and are pulled towards opposite poles of the cell . in telophase ii , nuclear membranes form around each set of chromosomes , and the chromosomes decondense . cytokinesis splits the chromosome sets into new cells , forming the final products of meiosis : four haploid cells in which each chromosome has just one chromatid . in humans , the products of meiosis are sperm or egg cells . how meiosis `` mixes and matches '' genes the gametes produced in meiosis are all haploid , but they 're not genetically identical . for example , take a look the meiosis ii diagram above , which shows the products of meiosis for a cell with $ 2n = 4 $ chromosomes . each gamete has a unique `` sample '' of the genetic material present in the starting cell . as it turns out , there are many more potential gamete types than just the four shown in the diagram , even for a cell with with only four chromosomes . the two main reason we can get many genetically different gametes are : crossing over . the points where homologues cross over and exchange genetic material are chosen more or less at random , and they will be different in each cell that goes through meiosis . if meiosis happens many times , as in humans , crossovers will happen at many different points . random orientation of homologue pairs . the random orientation of homologue pairs in metaphase i allows for the production of gametes with many different assortments of homologous chromosomes . in a human cell , the random orientation of homologue pairs alone allows for over $ 8 $ $ \text { million } $ different types of possible gametes $ ^7 $ . when we layer crossing over on top of this , the number of genetically different gametes that you—or any other person—can make is effectively infinite . check out the video on variation in a species to learn how genetic diversity generated by meiosis ( and fertilization ) is important in evolution and helps populations survive .
|
meiosis i before entering meiosis i , a cell must first go through interphase . as in mitosis , the cell grows during g $ _1 $ phase , copies all of its chromosomes during s phase , and prepares for division during g $ _2 $ phase . during prophase i , differences from mitosis begin to appear .
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does replication of germ cells in s-phase effect the ploidy ?
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introduction mitosis is used for almost all of your body ’ s cell division needs . it adds new cells during development and replaces old and worn-out cells throughout your life . the goal of mitosis is to produce daughter cells that are genetically identical to their mothers , with not a single chromosome more or less . meiosis , on the other hand , is used for just one purpose in the human body : the production of gametes—sex cells , or sperm and eggs . its goal is to make daughter cells with exactly half as many chromosomes as the starting cell . to put that another way , meiosis in humans is a division process that takes us from a diploid cell—one with two sets of chromosomes—to haploid cells—ones with a single set of chromosomes . in humans , the haploid cells made in meiosis are sperm and eggs . when a sperm and an egg join in fertilization , the two haploid sets of chromosomes form a complete diploid set : a new genome . phases of meiosis in many ways , meiosis is a lot like mitosis . the cell goes through similar stages and uses similar strategies to organize and separate chromosomes . in meiosis , however , the cell has a more complex task . it still needs to separate sister chromatids ( the two halves of a duplicated chromosome ) , as in mitosis . but it must also separate homologous chromosomes , the similar but nonidentical chromosome pairs an organism receives from its two parents . these goals are accomplished in meiosis using a two-step division process . homologue pairs separate during a first round of cell division , called meiosis i . sister chromatids separate during a second round , called meiosis ii . since cell division occurs twice during meiosis , one starting cell can produce four gametes ( eggs or sperm ) . in each round of division , cells go through four stages : prophase , metaphase , anaphase , and telophase . meiosis i before entering meiosis i , a cell must first go through interphase . as in mitosis , the cell grows during g $ _1 $ phase , copies all of its chromosomes during s phase , and prepares for division during g $ _2 $ phase . during prophase i , differences from mitosis begin to appear . as in mitosis , the chromosomes begin to condense , but in meiosis i , they also pair up . each chromosome carefully aligns with its homologue partner so that the two match up at corresponding positions along their full length . for instance , in the image below , the letters a , b , and c represent genes found at particular spots on the chromosome , with capital and lowercase letters for different forms , or alleles , of each gene . the dna is broken at the same spot on each homologue—here , between genes b and c—and reconnected in a criss-cross pattern so that the homologues exchange part of their dna . this process , in which homologous chromosomes trade parts , is called crossing over . it 's helped along by a protein structure called the synaptonemal complex that holds the homologues together . the chromosomes would actually be positioned one on top of the other—as in the image below—throughout crossing over ; they 're only shown side-by-side in the image above so that it 's easier to see the exchange of genetic material . you can see crossovers under a microscope as chiasmata , cross-shaped structures where homologues are linked together . chiasmata keep the homologues connected to each other after the synaptonemal complex breaks down , so each homologous pair needs at least one . it 's common for multiple crossovers ( up to $ 25 $ ! ) to take place for each homologue pair $ ^1 $ . the spots where crossovers happen are more or less random , leading to the formation of new , `` remixed '' chromosomes with unique combinations of alleles . after crossing over , the spindle begins to capture chromosomes and move them towards the center of the cell ( metaphase plate ) . this may seem familiar from mitosis , but there is a twist . each chromosome attaches to microtubules from just one pole of the spindle , and the two homologues of a pair bind to microtubules from opposite poles . so , during metaphase i , homologue pairs—not individual chromosomes—line up at the metaphase plate for separation . when the homologous pairs line up at the metaphase plate , the orientation of each pair is random . for instance , in the diagram above , the pink version of the big chromosome and the purple version of the little chromosome happen to be positioned towards the same pole and go into the same cell . but the orientation could have equally well been flipped , so that both purple chromosomes went into the cell together . this allows for the formation of gametes with different sets of homologues . in anaphase i , the homologues are pulled apart and move apart to opposite ends of the cell . the sister chromatids of each chromosome , however , remain attached to one another and do n't come apart . finally , in telophase i , the chromosomes arrive at opposite poles of the cell . in some organisms , the nuclear membrane re-forms and the chromosomes decondense , although in others , this step is skipped—since cells will soon go through another round of division , meiosis ii $ ^ { 2,3 } $ . cytokinesis usually occurs at the same time as telophase i , forming two haploid daughter cells . meiosis ii cells move from meiosis i to meiosis ii without copying their dna . meiosis ii is a shorter and simpler process than meiosis i , and you may find it helpful to think of meiosis ii as “ mitosis for haploid cells . '' the cells that enter meiosis ii are the ones made in meiosis i . these cells are haploid—have just one chromosome from each homologue pair—but their chromosomes still consist of two sister chromatids . in meiosis ii , the sister chromatids separate , making haploid cells with non-duplicated chromosomes . during prophase ii , chromosomes condense and the nuclear envelope breaks down , if needed . the centrosomes move apart , the spindle forms between them , and the spindle microtubules begin to capture chromosomes . the two sister chromatids of each chromosome are captured by microtubules from opposite spindle poles . in metaphase ii , the chromosomes line up individually along the metaphase plate . in anaphase ii , the sister chromatids separate and are pulled towards opposite poles of the cell . in telophase ii , nuclear membranes form around each set of chromosomes , and the chromosomes decondense . cytokinesis splits the chromosome sets into new cells , forming the final products of meiosis : four haploid cells in which each chromosome has just one chromatid . in humans , the products of meiosis are sperm or egg cells . how meiosis `` mixes and matches '' genes the gametes produced in meiosis are all haploid , but they 're not genetically identical . for example , take a look the meiosis ii diagram above , which shows the products of meiosis for a cell with $ 2n = 4 $ chromosomes . each gamete has a unique `` sample '' of the genetic material present in the starting cell . as it turns out , there are many more potential gamete types than just the four shown in the diagram , even for a cell with with only four chromosomes . the two main reason we can get many genetically different gametes are : crossing over . the points where homologues cross over and exchange genetic material are chosen more or less at random , and they will be different in each cell that goes through meiosis . if meiosis happens many times , as in humans , crossovers will happen at many different points . random orientation of homologue pairs . the random orientation of homologue pairs in metaphase i allows for the production of gametes with many different assortments of homologous chromosomes . in a human cell , the random orientation of homologue pairs alone allows for over $ 8 $ $ \text { million } $ different types of possible gametes $ ^7 $ . when we layer crossing over on top of this , the number of genetically different gametes that you—or any other person—can make is effectively infinite . check out the video on variation in a species to learn how genetic diversity generated by meiosis ( and fertilization ) is important in evolution and helps populations survive .
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in anaphase ii , the sister chromatids separate and are pulled towards opposite poles of the cell . in telophase ii , nuclear membranes form around each set of chromosomes , and the chromosomes decondense . cytokinesis splits the chromosome sets into new cells , forming the final products of meiosis : four haploid cells in which each chromosome has just one chromatid .
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how does the nuclear membrane re-form around each set of chormosomes after meoiosis ll ?
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introduction mitosis is used for almost all of your body ’ s cell division needs . it adds new cells during development and replaces old and worn-out cells throughout your life . the goal of mitosis is to produce daughter cells that are genetically identical to their mothers , with not a single chromosome more or less . meiosis , on the other hand , is used for just one purpose in the human body : the production of gametes—sex cells , or sperm and eggs . its goal is to make daughter cells with exactly half as many chromosomes as the starting cell . to put that another way , meiosis in humans is a division process that takes us from a diploid cell—one with two sets of chromosomes—to haploid cells—ones with a single set of chromosomes . in humans , the haploid cells made in meiosis are sperm and eggs . when a sperm and an egg join in fertilization , the two haploid sets of chromosomes form a complete diploid set : a new genome . phases of meiosis in many ways , meiosis is a lot like mitosis . the cell goes through similar stages and uses similar strategies to organize and separate chromosomes . in meiosis , however , the cell has a more complex task . it still needs to separate sister chromatids ( the two halves of a duplicated chromosome ) , as in mitosis . but it must also separate homologous chromosomes , the similar but nonidentical chromosome pairs an organism receives from its two parents . these goals are accomplished in meiosis using a two-step division process . homologue pairs separate during a first round of cell division , called meiosis i . sister chromatids separate during a second round , called meiosis ii . since cell division occurs twice during meiosis , one starting cell can produce four gametes ( eggs or sperm ) . in each round of division , cells go through four stages : prophase , metaphase , anaphase , and telophase . meiosis i before entering meiosis i , a cell must first go through interphase . as in mitosis , the cell grows during g $ _1 $ phase , copies all of its chromosomes during s phase , and prepares for division during g $ _2 $ phase . during prophase i , differences from mitosis begin to appear . as in mitosis , the chromosomes begin to condense , but in meiosis i , they also pair up . each chromosome carefully aligns with its homologue partner so that the two match up at corresponding positions along their full length . for instance , in the image below , the letters a , b , and c represent genes found at particular spots on the chromosome , with capital and lowercase letters for different forms , or alleles , of each gene . the dna is broken at the same spot on each homologue—here , between genes b and c—and reconnected in a criss-cross pattern so that the homologues exchange part of their dna . this process , in which homologous chromosomes trade parts , is called crossing over . it 's helped along by a protein structure called the synaptonemal complex that holds the homologues together . the chromosomes would actually be positioned one on top of the other—as in the image below—throughout crossing over ; they 're only shown side-by-side in the image above so that it 's easier to see the exchange of genetic material . you can see crossovers under a microscope as chiasmata , cross-shaped structures where homologues are linked together . chiasmata keep the homologues connected to each other after the synaptonemal complex breaks down , so each homologous pair needs at least one . it 's common for multiple crossovers ( up to $ 25 $ ! ) to take place for each homologue pair $ ^1 $ . the spots where crossovers happen are more or less random , leading to the formation of new , `` remixed '' chromosomes with unique combinations of alleles . after crossing over , the spindle begins to capture chromosomes and move them towards the center of the cell ( metaphase plate ) . this may seem familiar from mitosis , but there is a twist . each chromosome attaches to microtubules from just one pole of the spindle , and the two homologues of a pair bind to microtubules from opposite poles . so , during metaphase i , homologue pairs—not individual chromosomes—line up at the metaphase plate for separation . when the homologous pairs line up at the metaphase plate , the orientation of each pair is random . for instance , in the diagram above , the pink version of the big chromosome and the purple version of the little chromosome happen to be positioned towards the same pole and go into the same cell . but the orientation could have equally well been flipped , so that both purple chromosomes went into the cell together . this allows for the formation of gametes with different sets of homologues . in anaphase i , the homologues are pulled apart and move apart to opposite ends of the cell . the sister chromatids of each chromosome , however , remain attached to one another and do n't come apart . finally , in telophase i , the chromosomes arrive at opposite poles of the cell . in some organisms , the nuclear membrane re-forms and the chromosomes decondense , although in others , this step is skipped—since cells will soon go through another round of division , meiosis ii $ ^ { 2,3 } $ . cytokinesis usually occurs at the same time as telophase i , forming two haploid daughter cells . meiosis ii cells move from meiosis i to meiosis ii without copying their dna . meiosis ii is a shorter and simpler process than meiosis i , and you may find it helpful to think of meiosis ii as “ mitosis for haploid cells . '' the cells that enter meiosis ii are the ones made in meiosis i . these cells are haploid—have just one chromosome from each homologue pair—but their chromosomes still consist of two sister chromatids . in meiosis ii , the sister chromatids separate , making haploid cells with non-duplicated chromosomes . during prophase ii , chromosomes condense and the nuclear envelope breaks down , if needed . the centrosomes move apart , the spindle forms between them , and the spindle microtubules begin to capture chromosomes . the two sister chromatids of each chromosome are captured by microtubules from opposite spindle poles . in metaphase ii , the chromosomes line up individually along the metaphase plate . in anaphase ii , the sister chromatids separate and are pulled towards opposite poles of the cell . in telophase ii , nuclear membranes form around each set of chromosomes , and the chromosomes decondense . cytokinesis splits the chromosome sets into new cells , forming the final products of meiosis : four haploid cells in which each chromosome has just one chromatid . in humans , the products of meiosis are sperm or egg cells . how meiosis `` mixes and matches '' genes the gametes produced in meiosis are all haploid , but they 're not genetically identical . for example , take a look the meiosis ii diagram above , which shows the products of meiosis for a cell with $ 2n = 4 $ chromosomes . each gamete has a unique `` sample '' of the genetic material present in the starting cell . as it turns out , there are many more potential gamete types than just the four shown in the diagram , even for a cell with with only four chromosomes . the two main reason we can get many genetically different gametes are : crossing over . the points where homologues cross over and exchange genetic material are chosen more or less at random , and they will be different in each cell that goes through meiosis . if meiosis happens many times , as in humans , crossovers will happen at many different points . random orientation of homologue pairs . the random orientation of homologue pairs in metaphase i allows for the production of gametes with many different assortments of homologous chromosomes . in a human cell , the random orientation of homologue pairs alone allows for over $ 8 $ $ \text { million } $ different types of possible gametes $ ^7 $ . when we layer crossing over on top of this , the number of genetically different gametes that you—or any other person—can make is effectively infinite . check out the video on variation in a species to learn how genetic diversity generated by meiosis ( and fertilization ) is important in evolution and helps populations survive .
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in some organisms , the nuclear membrane re-forms and the chromosomes decondense , although in others , this step is skipped—since cells will soon go through another round of division , meiosis ii $ ^ { 2,3 } $ . cytokinesis usually occurs at the same time as telophase i , forming two haploid daughter cells . meiosis ii cells move from meiosis i to meiosis ii without copying their dna . meiosis ii is a shorter and simpler process than meiosis i , and you may find it helpful to think of meiosis ii as “ mitosis for haploid cells . ''
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if haploid cells are formed from a diploid cell in meiosis 1 and each resulting daughter cell becomes a haploid after meiosis 2 , would n't the dna be one quarter as opposed to half ?
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introduction mitosis is used for almost all of your body ’ s cell division needs . it adds new cells during development and replaces old and worn-out cells throughout your life . the goal of mitosis is to produce daughter cells that are genetically identical to their mothers , with not a single chromosome more or less . meiosis , on the other hand , is used for just one purpose in the human body : the production of gametes—sex cells , or sperm and eggs . its goal is to make daughter cells with exactly half as many chromosomes as the starting cell . to put that another way , meiosis in humans is a division process that takes us from a diploid cell—one with two sets of chromosomes—to haploid cells—ones with a single set of chromosomes . in humans , the haploid cells made in meiosis are sperm and eggs . when a sperm and an egg join in fertilization , the two haploid sets of chromosomes form a complete diploid set : a new genome . phases of meiosis in many ways , meiosis is a lot like mitosis . the cell goes through similar stages and uses similar strategies to organize and separate chromosomes . in meiosis , however , the cell has a more complex task . it still needs to separate sister chromatids ( the two halves of a duplicated chromosome ) , as in mitosis . but it must also separate homologous chromosomes , the similar but nonidentical chromosome pairs an organism receives from its two parents . these goals are accomplished in meiosis using a two-step division process . homologue pairs separate during a first round of cell division , called meiosis i . sister chromatids separate during a second round , called meiosis ii . since cell division occurs twice during meiosis , one starting cell can produce four gametes ( eggs or sperm ) . in each round of division , cells go through four stages : prophase , metaphase , anaphase , and telophase . meiosis i before entering meiosis i , a cell must first go through interphase . as in mitosis , the cell grows during g $ _1 $ phase , copies all of its chromosomes during s phase , and prepares for division during g $ _2 $ phase . during prophase i , differences from mitosis begin to appear . as in mitosis , the chromosomes begin to condense , but in meiosis i , they also pair up . each chromosome carefully aligns with its homologue partner so that the two match up at corresponding positions along their full length . for instance , in the image below , the letters a , b , and c represent genes found at particular spots on the chromosome , with capital and lowercase letters for different forms , or alleles , of each gene . the dna is broken at the same spot on each homologue—here , between genes b and c—and reconnected in a criss-cross pattern so that the homologues exchange part of their dna . this process , in which homologous chromosomes trade parts , is called crossing over . it 's helped along by a protein structure called the synaptonemal complex that holds the homologues together . the chromosomes would actually be positioned one on top of the other—as in the image below—throughout crossing over ; they 're only shown side-by-side in the image above so that it 's easier to see the exchange of genetic material . you can see crossovers under a microscope as chiasmata , cross-shaped structures where homologues are linked together . chiasmata keep the homologues connected to each other after the synaptonemal complex breaks down , so each homologous pair needs at least one . it 's common for multiple crossovers ( up to $ 25 $ ! ) to take place for each homologue pair $ ^1 $ . the spots where crossovers happen are more or less random , leading to the formation of new , `` remixed '' chromosomes with unique combinations of alleles . after crossing over , the spindle begins to capture chromosomes and move them towards the center of the cell ( metaphase plate ) . this may seem familiar from mitosis , but there is a twist . each chromosome attaches to microtubules from just one pole of the spindle , and the two homologues of a pair bind to microtubules from opposite poles . so , during metaphase i , homologue pairs—not individual chromosomes—line up at the metaphase plate for separation . when the homologous pairs line up at the metaphase plate , the orientation of each pair is random . for instance , in the diagram above , the pink version of the big chromosome and the purple version of the little chromosome happen to be positioned towards the same pole and go into the same cell . but the orientation could have equally well been flipped , so that both purple chromosomes went into the cell together . this allows for the formation of gametes with different sets of homologues . in anaphase i , the homologues are pulled apart and move apart to opposite ends of the cell . the sister chromatids of each chromosome , however , remain attached to one another and do n't come apart . finally , in telophase i , the chromosomes arrive at opposite poles of the cell . in some organisms , the nuclear membrane re-forms and the chromosomes decondense , although in others , this step is skipped—since cells will soon go through another round of division , meiosis ii $ ^ { 2,3 } $ . cytokinesis usually occurs at the same time as telophase i , forming two haploid daughter cells . meiosis ii cells move from meiosis i to meiosis ii without copying their dna . meiosis ii is a shorter and simpler process than meiosis i , and you may find it helpful to think of meiosis ii as “ mitosis for haploid cells . '' the cells that enter meiosis ii are the ones made in meiosis i . these cells are haploid—have just one chromosome from each homologue pair—but their chromosomes still consist of two sister chromatids . in meiosis ii , the sister chromatids separate , making haploid cells with non-duplicated chromosomes . during prophase ii , chromosomes condense and the nuclear envelope breaks down , if needed . the centrosomes move apart , the spindle forms between them , and the spindle microtubules begin to capture chromosomes . the two sister chromatids of each chromosome are captured by microtubules from opposite spindle poles . in metaphase ii , the chromosomes line up individually along the metaphase plate . in anaphase ii , the sister chromatids separate and are pulled towards opposite poles of the cell . in telophase ii , nuclear membranes form around each set of chromosomes , and the chromosomes decondense . cytokinesis splits the chromosome sets into new cells , forming the final products of meiosis : four haploid cells in which each chromosome has just one chromatid . in humans , the products of meiosis are sperm or egg cells . how meiosis `` mixes and matches '' genes the gametes produced in meiosis are all haploid , but they 're not genetically identical . for example , take a look the meiosis ii diagram above , which shows the products of meiosis for a cell with $ 2n = 4 $ chromosomes . each gamete has a unique `` sample '' of the genetic material present in the starting cell . as it turns out , there are many more potential gamete types than just the four shown in the diagram , even for a cell with with only four chromosomes . the two main reason we can get many genetically different gametes are : crossing over . the points where homologues cross over and exchange genetic material are chosen more or less at random , and they will be different in each cell that goes through meiosis . if meiosis happens many times , as in humans , crossovers will happen at many different points . random orientation of homologue pairs . the random orientation of homologue pairs in metaphase i allows for the production of gametes with many different assortments of homologous chromosomes . in a human cell , the random orientation of homologue pairs alone allows for over $ 8 $ $ \text { million } $ different types of possible gametes $ ^7 $ . when we layer crossing over on top of this , the number of genetically different gametes that you—or any other person—can make is effectively infinite . check out the video on variation in a species to learn how genetic diversity generated by meiosis ( and fertilization ) is important in evolution and helps populations survive .
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sister chromatids separate during a second round , called meiosis ii . since cell division occurs twice during meiosis , one starting cell can produce four gametes ( eggs or sperm ) . in each round of division , cells go through four stages : prophase , metaphase , anaphase , and telophase .
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what exactly are spindles made of and when does the cell know when to produce them ?
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introduction mitosis is used for almost all of your body ’ s cell division needs . it adds new cells during development and replaces old and worn-out cells throughout your life . the goal of mitosis is to produce daughter cells that are genetically identical to their mothers , with not a single chromosome more or less . meiosis , on the other hand , is used for just one purpose in the human body : the production of gametes—sex cells , or sperm and eggs . its goal is to make daughter cells with exactly half as many chromosomes as the starting cell . to put that another way , meiosis in humans is a division process that takes us from a diploid cell—one with two sets of chromosomes—to haploid cells—ones with a single set of chromosomes . in humans , the haploid cells made in meiosis are sperm and eggs . when a sperm and an egg join in fertilization , the two haploid sets of chromosomes form a complete diploid set : a new genome . phases of meiosis in many ways , meiosis is a lot like mitosis . the cell goes through similar stages and uses similar strategies to organize and separate chromosomes . in meiosis , however , the cell has a more complex task . it still needs to separate sister chromatids ( the two halves of a duplicated chromosome ) , as in mitosis . but it must also separate homologous chromosomes , the similar but nonidentical chromosome pairs an organism receives from its two parents . these goals are accomplished in meiosis using a two-step division process . homologue pairs separate during a first round of cell division , called meiosis i . sister chromatids separate during a second round , called meiosis ii . since cell division occurs twice during meiosis , one starting cell can produce four gametes ( eggs or sperm ) . in each round of division , cells go through four stages : prophase , metaphase , anaphase , and telophase . meiosis i before entering meiosis i , a cell must first go through interphase . as in mitosis , the cell grows during g $ _1 $ phase , copies all of its chromosomes during s phase , and prepares for division during g $ _2 $ phase . during prophase i , differences from mitosis begin to appear . as in mitosis , the chromosomes begin to condense , but in meiosis i , they also pair up . each chromosome carefully aligns with its homologue partner so that the two match up at corresponding positions along their full length . for instance , in the image below , the letters a , b , and c represent genes found at particular spots on the chromosome , with capital and lowercase letters for different forms , or alleles , of each gene . the dna is broken at the same spot on each homologue—here , between genes b and c—and reconnected in a criss-cross pattern so that the homologues exchange part of their dna . this process , in which homologous chromosomes trade parts , is called crossing over . it 's helped along by a protein structure called the synaptonemal complex that holds the homologues together . the chromosomes would actually be positioned one on top of the other—as in the image below—throughout crossing over ; they 're only shown side-by-side in the image above so that it 's easier to see the exchange of genetic material . you can see crossovers under a microscope as chiasmata , cross-shaped structures where homologues are linked together . chiasmata keep the homologues connected to each other after the synaptonemal complex breaks down , so each homologous pair needs at least one . it 's common for multiple crossovers ( up to $ 25 $ ! ) to take place for each homologue pair $ ^1 $ . the spots where crossovers happen are more or less random , leading to the formation of new , `` remixed '' chromosomes with unique combinations of alleles . after crossing over , the spindle begins to capture chromosomes and move them towards the center of the cell ( metaphase plate ) . this may seem familiar from mitosis , but there is a twist . each chromosome attaches to microtubules from just one pole of the spindle , and the two homologues of a pair bind to microtubules from opposite poles . so , during metaphase i , homologue pairs—not individual chromosomes—line up at the metaphase plate for separation . when the homologous pairs line up at the metaphase plate , the orientation of each pair is random . for instance , in the diagram above , the pink version of the big chromosome and the purple version of the little chromosome happen to be positioned towards the same pole and go into the same cell . but the orientation could have equally well been flipped , so that both purple chromosomes went into the cell together . this allows for the formation of gametes with different sets of homologues . in anaphase i , the homologues are pulled apart and move apart to opposite ends of the cell . the sister chromatids of each chromosome , however , remain attached to one another and do n't come apart . finally , in telophase i , the chromosomes arrive at opposite poles of the cell . in some organisms , the nuclear membrane re-forms and the chromosomes decondense , although in others , this step is skipped—since cells will soon go through another round of division , meiosis ii $ ^ { 2,3 } $ . cytokinesis usually occurs at the same time as telophase i , forming two haploid daughter cells . meiosis ii cells move from meiosis i to meiosis ii without copying their dna . meiosis ii is a shorter and simpler process than meiosis i , and you may find it helpful to think of meiosis ii as “ mitosis for haploid cells . '' the cells that enter meiosis ii are the ones made in meiosis i . these cells are haploid—have just one chromosome from each homologue pair—but their chromosomes still consist of two sister chromatids . in meiosis ii , the sister chromatids separate , making haploid cells with non-duplicated chromosomes . during prophase ii , chromosomes condense and the nuclear envelope breaks down , if needed . the centrosomes move apart , the spindle forms between them , and the spindle microtubules begin to capture chromosomes . the two sister chromatids of each chromosome are captured by microtubules from opposite spindle poles . in metaphase ii , the chromosomes line up individually along the metaphase plate . in anaphase ii , the sister chromatids separate and are pulled towards opposite poles of the cell . in telophase ii , nuclear membranes form around each set of chromosomes , and the chromosomes decondense . cytokinesis splits the chromosome sets into new cells , forming the final products of meiosis : four haploid cells in which each chromosome has just one chromatid . in humans , the products of meiosis are sperm or egg cells . how meiosis `` mixes and matches '' genes the gametes produced in meiosis are all haploid , but they 're not genetically identical . for example , take a look the meiosis ii diagram above , which shows the products of meiosis for a cell with $ 2n = 4 $ chromosomes . each gamete has a unique `` sample '' of the genetic material present in the starting cell . as it turns out , there are many more potential gamete types than just the four shown in the diagram , even for a cell with with only four chromosomes . the two main reason we can get many genetically different gametes are : crossing over . the points where homologues cross over and exchange genetic material are chosen more or less at random , and they will be different in each cell that goes through meiosis . if meiosis happens many times , as in humans , crossovers will happen at many different points . random orientation of homologue pairs . the random orientation of homologue pairs in metaphase i allows for the production of gametes with many different assortments of homologous chromosomes . in a human cell , the random orientation of homologue pairs alone allows for over $ 8 $ $ \text { million } $ different types of possible gametes $ ^7 $ . when we layer crossing over on top of this , the number of genetically different gametes that you—or any other person—can make is effectively infinite . check out the video on variation in a species to learn how genetic diversity generated by meiosis ( and fertilization ) is important in evolution and helps populations survive .
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the sister chromatids of each chromosome , however , remain attached to one another and do n't come apart . finally , in telophase i , the chromosomes arrive at opposite poles of the cell . in some organisms , the nuclear membrane re-forms and the chromosomes decondense , although in others , this step is skipped—since cells will soon go through another round of division , meiosis ii $ ^ { 2,3 } $ .
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in telophase i each cell contains 23 d-chromosomes ... that means that each cell contains 46 s-chromosomes so how does it contain haploid number ?
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introduction mitosis is used for almost all of your body ’ s cell division needs . it adds new cells during development and replaces old and worn-out cells throughout your life . the goal of mitosis is to produce daughter cells that are genetically identical to their mothers , with not a single chromosome more or less . meiosis , on the other hand , is used for just one purpose in the human body : the production of gametes—sex cells , or sperm and eggs . its goal is to make daughter cells with exactly half as many chromosomes as the starting cell . to put that another way , meiosis in humans is a division process that takes us from a diploid cell—one with two sets of chromosomes—to haploid cells—ones with a single set of chromosomes . in humans , the haploid cells made in meiosis are sperm and eggs . when a sperm and an egg join in fertilization , the two haploid sets of chromosomes form a complete diploid set : a new genome . phases of meiosis in many ways , meiosis is a lot like mitosis . the cell goes through similar stages and uses similar strategies to organize and separate chromosomes . in meiosis , however , the cell has a more complex task . it still needs to separate sister chromatids ( the two halves of a duplicated chromosome ) , as in mitosis . but it must also separate homologous chromosomes , the similar but nonidentical chromosome pairs an organism receives from its two parents . these goals are accomplished in meiosis using a two-step division process . homologue pairs separate during a first round of cell division , called meiosis i . sister chromatids separate during a second round , called meiosis ii . since cell division occurs twice during meiosis , one starting cell can produce four gametes ( eggs or sperm ) . in each round of division , cells go through four stages : prophase , metaphase , anaphase , and telophase . meiosis i before entering meiosis i , a cell must first go through interphase . as in mitosis , the cell grows during g $ _1 $ phase , copies all of its chromosomes during s phase , and prepares for division during g $ _2 $ phase . during prophase i , differences from mitosis begin to appear . as in mitosis , the chromosomes begin to condense , but in meiosis i , they also pair up . each chromosome carefully aligns with its homologue partner so that the two match up at corresponding positions along their full length . for instance , in the image below , the letters a , b , and c represent genes found at particular spots on the chromosome , with capital and lowercase letters for different forms , or alleles , of each gene . the dna is broken at the same spot on each homologue—here , between genes b and c—and reconnected in a criss-cross pattern so that the homologues exchange part of their dna . this process , in which homologous chromosomes trade parts , is called crossing over . it 's helped along by a protein structure called the synaptonemal complex that holds the homologues together . the chromosomes would actually be positioned one on top of the other—as in the image below—throughout crossing over ; they 're only shown side-by-side in the image above so that it 's easier to see the exchange of genetic material . you can see crossovers under a microscope as chiasmata , cross-shaped structures where homologues are linked together . chiasmata keep the homologues connected to each other after the synaptonemal complex breaks down , so each homologous pair needs at least one . it 's common for multiple crossovers ( up to $ 25 $ ! ) to take place for each homologue pair $ ^1 $ . the spots where crossovers happen are more or less random , leading to the formation of new , `` remixed '' chromosomes with unique combinations of alleles . after crossing over , the spindle begins to capture chromosomes and move them towards the center of the cell ( metaphase plate ) . this may seem familiar from mitosis , but there is a twist . each chromosome attaches to microtubules from just one pole of the spindle , and the two homologues of a pair bind to microtubules from opposite poles . so , during metaphase i , homologue pairs—not individual chromosomes—line up at the metaphase plate for separation . when the homologous pairs line up at the metaphase plate , the orientation of each pair is random . for instance , in the diagram above , the pink version of the big chromosome and the purple version of the little chromosome happen to be positioned towards the same pole and go into the same cell . but the orientation could have equally well been flipped , so that both purple chromosomes went into the cell together . this allows for the formation of gametes with different sets of homologues . in anaphase i , the homologues are pulled apart and move apart to opposite ends of the cell . the sister chromatids of each chromosome , however , remain attached to one another and do n't come apart . finally , in telophase i , the chromosomes arrive at opposite poles of the cell . in some organisms , the nuclear membrane re-forms and the chromosomes decondense , although in others , this step is skipped—since cells will soon go through another round of division , meiosis ii $ ^ { 2,3 } $ . cytokinesis usually occurs at the same time as telophase i , forming two haploid daughter cells . meiosis ii cells move from meiosis i to meiosis ii without copying their dna . meiosis ii is a shorter and simpler process than meiosis i , and you may find it helpful to think of meiosis ii as “ mitosis for haploid cells . '' the cells that enter meiosis ii are the ones made in meiosis i . these cells are haploid—have just one chromosome from each homologue pair—but their chromosomes still consist of two sister chromatids . in meiosis ii , the sister chromatids separate , making haploid cells with non-duplicated chromosomes . during prophase ii , chromosomes condense and the nuclear envelope breaks down , if needed . the centrosomes move apart , the spindle forms between them , and the spindle microtubules begin to capture chromosomes . the two sister chromatids of each chromosome are captured by microtubules from opposite spindle poles . in metaphase ii , the chromosomes line up individually along the metaphase plate . in anaphase ii , the sister chromatids separate and are pulled towards opposite poles of the cell . in telophase ii , nuclear membranes form around each set of chromosomes , and the chromosomes decondense . cytokinesis splits the chromosome sets into new cells , forming the final products of meiosis : four haploid cells in which each chromosome has just one chromatid . in humans , the products of meiosis are sperm or egg cells . how meiosis `` mixes and matches '' genes the gametes produced in meiosis are all haploid , but they 're not genetically identical . for example , take a look the meiosis ii diagram above , which shows the products of meiosis for a cell with $ 2n = 4 $ chromosomes . each gamete has a unique `` sample '' of the genetic material present in the starting cell . as it turns out , there are many more potential gamete types than just the four shown in the diagram , even for a cell with with only four chromosomes . the two main reason we can get many genetically different gametes are : crossing over . the points where homologues cross over and exchange genetic material are chosen more or less at random , and they will be different in each cell that goes through meiosis . if meiosis happens many times , as in humans , crossovers will happen at many different points . random orientation of homologue pairs . the random orientation of homologue pairs in metaphase i allows for the production of gametes with many different assortments of homologous chromosomes . in a human cell , the random orientation of homologue pairs alone allows for over $ 8 $ $ \text { million } $ different types of possible gametes $ ^7 $ . when we layer crossing over on top of this , the number of genetically different gametes that you—or any other person—can make is effectively infinite . check out the video on variation in a species to learn how genetic diversity generated by meiosis ( and fertilization ) is important in evolution and helps populations survive .
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these goals are accomplished in meiosis using a two-step division process . homologue pairs separate during a first round of cell division , called meiosis i . sister chromatids separate during a second round , called meiosis ii .
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if you have an organism that has both , sexual and asexual , types of reproduction , what will happen to the pairs of chromosomes of a cell that was born from an asexual cycle and is now going through meiosis ?
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introduction mitosis is used for almost all of your body ’ s cell division needs . it adds new cells during development and replaces old and worn-out cells throughout your life . the goal of mitosis is to produce daughter cells that are genetically identical to their mothers , with not a single chromosome more or less . meiosis , on the other hand , is used for just one purpose in the human body : the production of gametes—sex cells , or sperm and eggs . its goal is to make daughter cells with exactly half as many chromosomes as the starting cell . to put that another way , meiosis in humans is a division process that takes us from a diploid cell—one with two sets of chromosomes—to haploid cells—ones with a single set of chromosomes . in humans , the haploid cells made in meiosis are sperm and eggs . when a sperm and an egg join in fertilization , the two haploid sets of chromosomes form a complete diploid set : a new genome . phases of meiosis in many ways , meiosis is a lot like mitosis . the cell goes through similar stages and uses similar strategies to organize and separate chromosomes . in meiosis , however , the cell has a more complex task . it still needs to separate sister chromatids ( the two halves of a duplicated chromosome ) , as in mitosis . but it must also separate homologous chromosomes , the similar but nonidentical chromosome pairs an organism receives from its two parents . these goals are accomplished in meiosis using a two-step division process . homologue pairs separate during a first round of cell division , called meiosis i . sister chromatids separate during a second round , called meiosis ii . since cell division occurs twice during meiosis , one starting cell can produce four gametes ( eggs or sperm ) . in each round of division , cells go through four stages : prophase , metaphase , anaphase , and telophase . meiosis i before entering meiosis i , a cell must first go through interphase . as in mitosis , the cell grows during g $ _1 $ phase , copies all of its chromosomes during s phase , and prepares for division during g $ _2 $ phase . during prophase i , differences from mitosis begin to appear . as in mitosis , the chromosomes begin to condense , but in meiosis i , they also pair up . each chromosome carefully aligns with its homologue partner so that the two match up at corresponding positions along their full length . for instance , in the image below , the letters a , b , and c represent genes found at particular spots on the chromosome , with capital and lowercase letters for different forms , or alleles , of each gene . the dna is broken at the same spot on each homologue—here , between genes b and c—and reconnected in a criss-cross pattern so that the homologues exchange part of their dna . this process , in which homologous chromosomes trade parts , is called crossing over . it 's helped along by a protein structure called the synaptonemal complex that holds the homologues together . the chromosomes would actually be positioned one on top of the other—as in the image below—throughout crossing over ; they 're only shown side-by-side in the image above so that it 's easier to see the exchange of genetic material . you can see crossovers under a microscope as chiasmata , cross-shaped structures where homologues are linked together . chiasmata keep the homologues connected to each other after the synaptonemal complex breaks down , so each homologous pair needs at least one . it 's common for multiple crossovers ( up to $ 25 $ ! ) to take place for each homologue pair $ ^1 $ . the spots where crossovers happen are more or less random , leading to the formation of new , `` remixed '' chromosomes with unique combinations of alleles . after crossing over , the spindle begins to capture chromosomes and move them towards the center of the cell ( metaphase plate ) . this may seem familiar from mitosis , but there is a twist . each chromosome attaches to microtubules from just one pole of the spindle , and the two homologues of a pair bind to microtubules from opposite poles . so , during metaphase i , homologue pairs—not individual chromosomes—line up at the metaphase plate for separation . when the homologous pairs line up at the metaphase plate , the orientation of each pair is random . for instance , in the diagram above , the pink version of the big chromosome and the purple version of the little chromosome happen to be positioned towards the same pole and go into the same cell . but the orientation could have equally well been flipped , so that both purple chromosomes went into the cell together . this allows for the formation of gametes with different sets of homologues . in anaphase i , the homologues are pulled apart and move apart to opposite ends of the cell . the sister chromatids of each chromosome , however , remain attached to one another and do n't come apart . finally , in telophase i , the chromosomes arrive at opposite poles of the cell . in some organisms , the nuclear membrane re-forms and the chromosomes decondense , although in others , this step is skipped—since cells will soon go through another round of division , meiosis ii $ ^ { 2,3 } $ . cytokinesis usually occurs at the same time as telophase i , forming two haploid daughter cells . meiosis ii cells move from meiosis i to meiosis ii without copying their dna . meiosis ii is a shorter and simpler process than meiosis i , and you may find it helpful to think of meiosis ii as “ mitosis for haploid cells . '' the cells that enter meiosis ii are the ones made in meiosis i . these cells are haploid—have just one chromosome from each homologue pair—but their chromosomes still consist of two sister chromatids . in meiosis ii , the sister chromatids separate , making haploid cells with non-duplicated chromosomes . during prophase ii , chromosomes condense and the nuclear envelope breaks down , if needed . the centrosomes move apart , the spindle forms between them , and the spindle microtubules begin to capture chromosomes . the two sister chromatids of each chromosome are captured by microtubules from opposite spindle poles . in metaphase ii , the chromosomes line up individually along the metaphase plate . in anaphase ii , the sister chromatids separate and are pulled towards opposite poles of the cell . in telophase ii , nuclear membranes form around each set of chromosomes , and the chromosomes decondense . cytokinesis splits the chromosome sets into new cells , forming the final products of meiosis : four haploid cells in which each chromosome has just one chromatid . in humans , the products of meiosis are sperm or egg cells . how meiosis `` mixes and matches '' genes the gametes produced in meiosis are all haploid , but they 're not genetically identical . for example , take a look the meiosis ii diagram above , which shows the products of meiosis for a cell with $ 2n = 4 $ chromosomes . each gamete has a unique `` sample '' of the genetic material present in the starting cell . as it turns out , there are many more potential gamete types than just the four shown in the diagram , even for a cell with with only four chromosomes . the two main reason we can get many genetically different gametes are : crossing over . the points where homologues cross over and exchange genetic material are chosen more or less at random , and they will be different in each cell that goes through meiosis . if meiosis happens many times , as in humans , crossovers will happen at many different points . random orientation of homologue pairs . the random orientation of homologue pairs in metaphase i allows for the production of gametes with many different assortments of homologous chromosomes . in a human cell , the random orientation of homologue pairs alone allows for over $ 8 $ $ \text { million } $ different types of possible gametes $ ^7 $ . when we layer crossing over on top of this , the number of genetically different gametes that you—or any other person—can make is effectively infinite . check out the video on variation in a species to learn how genetic diversity generated by meiosis ( and fertilization ) is important in evolution and helps populations survive .
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these goals are accomplished in meiosis using a two-step division process . homologue pairs separate during a first round of cell division , called meiosis i . sister chromatids separate during a second round , called meiosis ii .
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why do the diagrams show the original cell with 2 pairs of chromosomes ?
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introduction mitosis is used for almost all of your body ’ s cell division needs . it adds new cells during development and replaces old and worn-out cells throughout your life . the goal of mitosis is to produce daughter cells that are genetically identical to their mothers , with not a single chromosome more or less . meiosis , on the other hand , is used for just one purpose in the human body : the production of gametes—sex cells , or sperm and eggs . its goal is to make daughter cells with exactly half as many chromosomes as the starting cell . to put that another way , meiosis in humans is a division process that takes us from a diploid cell—one with two sets of chromosomes—to haploid cells—ones with a single set of chromosomes . in humans , the haploid cells made in meiosis are sperm and eggs . when a sperm and an egg join in fertilization , the two haploid sets of chromosomes form a complete diploid set : a new genome . phases of meiosis in many ways , meiosis is a lot like mitosis . the cell goes through similar stages and uses similar strategies to organize and separate chromosomes . in meiosis , however , the cell has a more complex task . it still needs to separate sister chromatids ( the two halves of a duplicated chromosome ) , as in mitosis . but it must also separate homologous chromosomes , the similar but nonidentical chromosome pairs an organism receives from its two parents . these goals are accomplished in meiosis using a two-step division process . homologue pairs separate during a first round of cell division , called meiosis i . sister chromatids separate during a second round , called meiosis ii . since cell division occurs twice during meiosis , one starting cell can produce four gametes ( eggs or sperm ) . in each round of division , cells go through four stages : prophase , metaphase , anaphase , and telophase . meiosis i before entering meiosis i , a cell must first go through interphase . as in mitosis , the cell grows during g $ _1 $ phase , copies all of its chromosomes during s phase , and prepares for division during g $ _2 $ phase . during prophase i , differences from mitosis begin to appear . as in mitosis , the chromosomes begin to condense , but in meiosis i , they also pair up . each chromosome carefully aligns with its homologue partner so that the two match up at corresponding positions along their full length . for instance , in the image below , the letters a , b , and c represent genes found at particular spots on the chromosome , with capital and lowercase letters for different forms , or alleles , of each gene . the dna is broken at the same spot on each homologue—here , between genes b and c—and reconnected in a criss-cross pattern so that the homologues exchange part of their dna . this process , in which homologous chromosomes trade parts , is called crossing over . it 's helped along by a protein structure called the synaptonemal complex that holds the homologues together . the chromosomes would actually be positioned one on top of the other—as in the image below—throughout crossing over ; they 're only shown side-by-side in the image above so that it 's easier to see the exchange of genetic material . you can see crossovers under a microscope as chiasmata , cross-shaped structures where homologues are linked together . chiasmata keep the homologues connected to each other after the synaptonemal complex breaks down , so each homologous pair needs at least one . it 's common for multiple crossovers ( up to $ 25 $ ! ) to take place for each homologue pair $ ^1 $ . the spots where crossovers happen are more or less random , leading to the formation of new , `` remixed '' chromosomes with unique combinations of alleles . after crossing over , the spindle begins to capture chromosomes and move them towards the center of the cell ( metaphase plate ) . this may seem familiar from mitosis , but there is a twist . each chromosome attaches to microtubules from just one pole of the spindle , and the two homologues of a pair bind to microtubules from opposite poles . so , during metaphase i , homologue pairs—not individual chromosomes—line up at the metaphase plate for separation . when the homologous pairs line up at the metaphase plate , the orientation of each pair is random . for instance , in the diagram above , the pink version of the big chromosome and the purple version of the little chromosome happen to be positioned towards the same pole and go into the same cell . but the orientation could have equally well been flipped , so that both purple chromosomes went into the cell together . this allows for the formation of gametes with different sets of homologues . in anaphase i , the homologues are pulled apart and move apart to opposite ends of the cell . the sister chromatids of each chromosome , however , remain attached to one another and do n't come apart . finally , in telophase i , the chromosomes arrive at opposite poles of the cell . in some organisms , the nuclear membrane re-forms and the chromosomes decondense , although in others , this step is skipped—since cells will soon go through another round of division , meiosis ii $ ^ { 2,3 } $ . cytokinesis usually occurs at the same time as telophase i , forming two haploid daughter cells . meiosis ii cells move from meiosis i to meiosis ii without copying their dna . meiosis ii is a shorter and simpler process than meiosis i , and you may find it helpful to think of meiosis ii as “ mitosis for haploid cells . '' the cells that enter meiosis ii are the ones made in meiosis i . these cells are haploid—have just one chromosome from each homologue pair—but their chromosomes still consist of two sister chromatids . in meiosis ii , the sister chromatids separate , making haploid cells with non-duplicated chromosomes . during prophase ii , chromosomes condense and the nuclear envelope breaks down , if needed . the centrosomes move apart , the spindle forms between them , and the spindle microtubules begin to capture chromosomes . the two sister chromatids of each chromosome are captured by microtubules from opposite spindle poles . in metaphase ii , the chromosomes line up individually along the metaphase plate . in anaphase ii , the sister chromatids separate and are pulled towards opposite poles of the cell . in telophase ii , nuclear membranes form around each set of chromosomes , and the chromosomes decondense . cytokinesis splits the chromosome sets into new cells , forming the final products of meiosis : four haploid cells in which each chromosome has just one chromatid . in humans , the products of meiosis are sperm or egg cells . how meiosis `` mixes and matches '' genes the gametes produced in meiosis are all haploid , but they 're not genetically identical . for example , take a look the meiosis ii diagram above , which shows the products of meiosis for a cell with $ 2n = 4 $ chromosomes . each gamete has a unique `` sample '' of the genetic material present in the starting cell . as it turns out , there are many more potential gamete types than just the four shown in the diagram , even for a cell with with only four chromosomes . the two main reason we can get many genetically different gametes are : crossing over . the points where homologues cross over and exchange genetic material are chosen more or less at random , and they will be different in each cell that goes through meiosis . if meiosis happens many times , as in humans , crossovers will happen at many different points . random orientation of homologue pairs . the random orientation of homologue pairs in metaphase i allows for the production of gametes with many different assortments of homologous chromosomes . in a human cell , the random orientation of homologue pairs alone allows for over $ 8 $ $ \text { million } $ different types of possible gametes $ ^7 $ . when we layer crossing over on top of this , the number of genetically different gametes that you—or any other person—can make is effectively infinite . check out the video on variation in a species to learn how genetic diversity generated by meiosis ( and fertilization ) is important in evolution and helps populations survive .
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it 's common for multiple crossovers ( up to $ 25 $ ! ) to take place for each homologue pair $ ^1 $ . the spots where crossovers happen are more or less random , leading to the formation of new , `` remixed '' chromosomes with unique combinations of alleles .
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what is a homologue pair ?
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introduction mitosis is used for almost all of your body ’ s cell division needs . it adds new cells during development and replaces old and worn-out cells throughout your life . the goal of mitosis is to produce daughter cells that are genetically identical to their mothers , with not a single chromosome more or less . meiosis , on the other hand , is used for just one purpose in the human body : the production of gametes—sex cells , or sperm and eggs . its goal is to make daughter cells with exactly half as many chromosomes as the starting cell . to put that another way , meiosis in humans is a division process that takes us from a diploid cell—one with two sets of chromosomes—to haploid cells—ones with a single set of chromosomes . in humans , the haploid cells made in meiosis are sperm and eggs . when a sperm and an egg join in fertilization , the two haploid sets of chromosomes form a complete diploid set : a new genome . phases of meiosis in many ways , meiosis is a lot like mitosis . the cell goes through similar stages and uses similar strategies to organize and separate chromosomes . in meiosis , however , the cell has a more complex task . it still needs to separate sister chromatids ( the two halves of a duplicated chromosome ) , as in mitosis . but it must also separate homologous chromosomes , the similar but nonidentical chromosome pairs an organism receives from its two parents . these goals are accomplished in meiosis using a two-step division process . homologue pairs separate during a first round of cell division , called meiosis i . sister chromatids separate during a second round , called meiosis ii . since cell division occurs twice during meiosis , one starting cell can produce four gametes ( eggs or sperm ) . in each round of division , cells go through four stages : prophase , metaphase , anaphase , and telophase . meiosis i before entering meiosis i , a cell must first go through interphase . as in mitosis , the cell grows during g $ _1 $ phase , copies all of its chromosomes during s phase , and prepares for division during g $ _2 $ phase . during prophase i , differences from mitosis begin to appear . as in mitosis , the chromosomes begin to condense , but in meiosis i , they also pair up . each chromosome carefully aligns with its homologue partner so that the two match up at corresponding positions along their full length . for instance , in the image below , the letters a , b , and c represent genes found at particular spots on the chromosome , with capital and lowercase letters for different forms , or alleles , of each gene . the dna is broken at the same spot on each homologue—here , between genes b and c—and reconnected in a criss-cross pattern so that the homologues exchange part of their dna . this process , in which homologous chromosomes trade parts , is called crossing over . it 's helped along by a protein structure called the synaptonemal complex that holds the homologues together . the chromosomes would actually be positioned one on top of the other—as in the image below—throughout crossing over ; they 're only shown side-by-side in the image above so that it 's easier to see the exchange of genetic material . you can see crossovers under a microscope as chiasmata , cross-shaped structures where homologues are linked together . chiasmata keep the homologues connected to each other after the synaptonemal complex breaks down , so each homologous pair needs at least one . it 's common for multiple crossovers ( up to $ 25 $ ! ) to take place for each homologue pair $ ^1 $ . the spots where crossovers happen are more or less random , leading to the formation of new , `` remixed '' chromosomes with unique combinations of alleles . after crossing over , the spindle begins to capture chromosomes and move them towards the center of the cell ( metaphase plate ) . this may seem familiar from mitosis , but there is a twist . each chromosome attaches to microtubules from just one pole of the spindle , and the two homologues of a pair bind to microtubules from opposite poles . so , during metaphase i , homologue pairs—not individual chromosomes—line up at the metaphase plate for separation . when the homologous pairs line up at the metaphase plate , the orientation of each pair is random . for instance , in the diagram above , the pink version of the big chromosome and the purple version of the little chromosome happen to be positioned towards the same pole and go into the same cell . but the orientation could have equally well been flipped , so that both purple chromosomes went into the cell together . this allows for the formation of gametes with different sets of homologues . in anaphase i , the homologues are pulled apart and move apart to opposite ends of the cell . the sister chromatids of each chromosome , however , remain attached to one another and do n't come apart . finally , in telophase i , the chromosomes arrive at opposite poles of the cell . in some organisms , the nuclear membrane re-forms and the chromosomes decondense , although in others , this step is skipped—since cells will soon go through another round of division , meiosis ii $ ^ { 2,3 } $ . cytokinesis usually occurs at the same time as telophase i , forming two haploid daughter cells . meiosis ii cells move from meiosis i to meiosis ii without copying their dna . meiosis ii is a shorter and simpler process than meiosis i , and you may find it helpful to think of meiosis ii as “ mitosis for haploid cells . '' the cells that enter meiosis ii are the ones made in meiosis i . these cells are haploid—have just one chromosome from each homologue pair—but their chromosomes still consist of two sister chromatids . in meiosis ii , the sister chromatids separate , making haploid cells with non-duplicated chromosomes . during prophase ii , chromosomes condense and the nuclear envelope breaks down , if needed . the centrosomes move apart , the spindle forms between them , and the spindle microtubules begin to capture chromosomes . the two sister chromatids of each chromosome are captured by microtubules from opposite spindle poles . in metaphase ii , the chromosomes line up individually along the metaphase plate . in anaphase ii , the sister chromatids separate and are pulled towards opposite poles of the cell . in telophase ii , nuclear membranes form around each set of chromosomes , and the chromosomes decondense . cytokinesis splits the chromosome sets into new cells , forming the final products of meiosis : four haploid cells in which each chromosome has just one chromatid . in humans , the products of meiosis are sperm or egg cells . how meiosis `` mixes and matches '' genes the gametes produced in meiosis are all haploid , but they 're not genetically identical . for example , take a look the meiosis ii diagram above , which shows the products of meiosis for a cell with $ 2n = 4 $ chromosomes . each gamete has a unique `` sample '' of the genetic material present in the starting cell . as it turns out , there are many more potential gamete types than just the four shown in the diagram , even for a cell with with only four chromosomes . the two main reason we can get many genetically different gametes are : crossing over . the points where homologues cross over and exchange genetic material are chosen more or less at random , and they will be different in each cell that goes through meiosis . if meiosis happens many times , as in humans , crossovers will happen at many different points . random orientation of homologue pairs . the random orientation of homologue pairs in metaphase i allows for the production of gametes with many different assortments of homologous chromosomes . in a human cell , the random orientation of homologue pairs alone allows for over $ 8 $ $ \text { million } $ different types of possible gametes $ ^7 $ . when we layer crossing over on top of this , the number of genetically different gametes that you—or any other person—can make is effectively infinite . check out the video on variation in a species to learn how genetic diversity generated by meiosis ( and fertilization ) is important in evolution and helps populations survive .
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the chromosomes would actually be positioned one on top of the other—as in the image below—throughout crossing over ; they 're only shown side-by-side in the image above so that it 's easier to see the exchange of genetic material . you can see crossovers under a microscope as chiasmata , cross-shaped structures where homologues are linked together . chiasmata keep the homologues connected to each other after the synaptonemal complex breaks down , so each homologous pair needs at least one .
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are chiasmata found at certain places ?
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introduction mitosis is used for almost all of your body ’ s cell division needs . it adds new cells during development and replaces old and worn-out cells throughout your life . the goal of mitosis is to produce daughter cells that are genetically identical to their mothers , with not a single chromosome more or less . meiosis , on the other hand , is used for just one purpose in the human body : the production of gametes—sex cells , or sperm and eggs . its goal is to make daughter cells with exactly half as many chromosomes as the starting cell . to put that another way , meiosis in humans is a division process that takes us from a diploid cell—one with two sets of chromosomes—to haploid cells—ones with a single set of chromosomes . in humans , the haploid cells made in meiosis are sperm and eggs . when a sperm and an egg join in fertilization , the two haploid sets of chromosomes form a complete diploid set : a new genome . phases of meiosis in many ways , meiosis is a lot like mitosis . the cell goes through similar stages and uses similar strategies to organize and separate chromosomes . in meiosis , however , the cell has a more complex task . it still needs to separate sister chromatids ( the two halves of a duplicated chromosome ) , as in mitosis . but it must also separate homologous chromosomes , the similar but nonidentical chromosome pairs an organism receives from its two parents . these goals are accomplished in meiosis using a two-step division process . homologue pairs separate during a first round of cell division , called meiosis i . sister chromatids separate during a second round , called meiosis ii . since cell division occurs twice during meiosis , one starting cell can produce four gametes ( eggs or sperm ) . in each round of division , cells go through four stages : prophase , metaphase , anaphase , and telophase . meiosis i before entering meiosis i , a cell must first go through interphase . as in mitosis , the cell grows during g $ _1 $ phase , copies all of its chromosomes during s phase , and prepares for division during g $ _2 $ phase . during prophase i , differences from mitosis begin to appear . as in mitosis , the chromosomes begin to condense , but in meiosis i , they also pair up . each chromosome carefully aligns with its homologue partner so that the two match up at corresponding positions along their full length . for instance , in the image below , the letters a , b , and c represent genes found at particular spots on the chromosome , with capital and lowercase letters for different forms , or alleles , of each gene . the dna is broken at the same spot on each homologue—here , between genes b and c—and reconnected in a criss-cross pattern so that the homologues exchange part of their dna . this process , in which homologous chromosomes trade parts , is called crossing over . it 's helped along by a protein structure called the synaptonemal complex that holds the homologues together . the chromosomes would actually be positioned one on top of the other—as in the image below—throughout crossing over ; they 're only shown side-by-side in the image above so that it 's easier to see the exchange of genetic material . you can see crossovers under a microscope as chiasmata , cross-shaped structures where homologues are linked together . chiasmata keep the homologues connected to each other after the synaptonemal complex breaks down , so each homologous pair needs at least one . it 's common for multiple crossovers ( up to $ 25 $ ! ) to take place for each homologue pair $ ^1 $ . the spots where crossovers happen are more or less random , leading to the formation of new , `` remixed '' chromosomes with unique combinations of alleles . after crossing over , the spindle begins to capture chromosomes and move them towards the center of the cell ( metaphase plate ) . this may seem familiar from mitosis , but there is a twist . each chromosome attaches to microtubules from just one pole of the spindle , and the two homologues of a pair bind to microtubules from opposite poles . so , during metaphase i , homologue pairs—not individual chromosomes—line up at the metaphase plate for separation . when the homologous pairs line up at the metaphase plate , the orientation of each pair is random . for instance , in the diagram above , the pink version of the big chromosome and the purple version of the little chromosome happen to be positioned towards the same pole and go into the same cell . but the orientation could have equally well been flipped , so that both purple chromosomes went into the cell together . this allows for the formation of gametes with different sets of homologues . in anaphase i , the homologues are pulled apart and move apart to opposite ends of the cell . the sister chromatids of each chromosome , however , remain attached to one another and do n't come apart . finally , in telophase i , the chromosomes arrive at opposite poles of the cell . in some organisms , the nuclear membrane re-forms and the chromosomes decondense , although in others , this step is skipped—since cells will soon go through another round of division , meiosis ii $ ^ { 2,3 } $ . cytokinesis usually occurs at the same time as telophase i , forming two haploid daughter cells . meiosis ii cells move from meiosis i to meiosis ii without copying their dna . meiosis ii is a shorter and simpler process than meiosis i , and you may find it helpful to think of meiosis ii as “ mitosis for haploid cells . '' the cells that enter meiosis ii are the ones made in meiosis i . these cells are haploid—have just one chromosome from each homologue pair—but their chromosomes still consist of two sister chromatids . in meiosis ii , the sister chromatids separate , making haploid cells with non-duplicated chromosomes . during prophase ii , chromosomes condense and the nuclear envelope breaks down , if needed . the centrosomes move apart , the spindle forms between them , and the spindle microtubules begin to capture chromosomes . the two sister chromatids of each chromosome are captured by microtubules from opposite spindle poles . in metaphase ii , the chromosomes line up individually along the metaphase plate . in anaphase ii , the sister chromatids separate and are pulled towards opposite poles of the cell . in telophase ii , nuclear membranes form around each set of chromosomes , and the chromosomes decondense . cytokinesis splits the chromosome sets into new cells , forming the final products of meiosis : four haploid cells in which each chromosome has just one chromatid . in humans , the products of meiosis are sperm or egg cells . how meiosis `` mixes and matches '' genes the gametes produced in meiosis are all haploid , but they 're not genetically identical . for example , take a look the meiosis ii diagram above , which shows the products of meiosis for a cell with $ 2n = 4 $ chromosomes . each gamete has a unique `` sample '' of the genetic material present in the starting cell . as it turns out , there are many more potential gamete types than just the four shown in the diagram , even for a cell with with only four chromosomes . the two main reason we can get many genetically different gametes are : crossing over . the points where homologues cross over and exchange genetic material are chosen more or less at random , and they will be different in each cell that goes through meiosis . if meiosis happens many times , as in humans , crossovers will happen at many different points . random orientation of homologue pairs . the random orientation of homologue pairs in metaphase i allows for the production of gametes with many different assortments of homologous chromosomes . in a human cell , the random orientation of homologue pairs alone allows for over $ 8 $ $ \text { million } $ different types of possible gametes $ ^7 $ . when we layer crossing over on top of this , the number of genetically different gametes that you—or any other person—can make is effectively infinite . check out the video on variation in a species to learn how genetic diversity generated by meiosis ( and fertilization ) is important in evolution and helps populations survive .
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cytokinesis usually occurs at the same time as telophase i , forming two haploid daughter cells . meiosis ii cells move from meiosis i to meiosis ii without copying their dna . meiosis ii is a shorter and simpler process than meiosis i , and you may find it helpful to think of meiosis ii as “ mitosis for haploid cells . '' the cells that enter meiosis ii are the ones made in meiosis i .
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and i think hybrids are sterile because they do not have homologous chromosomes , but what stage of meiosis is affected ?
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introduction mitosis is used for almost all of your body ’ s cell division needs . it adds new cells during development and replaces old and worn-out cells throughout your life . the goal of mitosis is to produce daughter cells that are genetically identical to their mothers , with not a single chromosome more or less . meiosis , on the other hand , is used for just one purpose in the human body : the production of gametes—sex cells , or sperm and eggs . its goal is to make daughter cells with exactly half as many chromosomes as the starting cell . to put that another way , meiosis in humans is a division process that takes us from a diploid cell—one with two sets of chromosomes—to haploid cells—ones with a single set of chromosomes . in humans , the haploid cells made in meiosis are sperm and eggs . when a sperm and an egg join in fertilization , the two haploid sets of chromosomes form a complete diploid set : a new genome . phases of meiosis in many ways , meiosis is a lot like mitosis . the cell goes through similar stages and uses similar strategies to organize and separate chromosomes . in meiosis , however , the cell has a more complex task . it still needs to separate sister chromatids ( the two halves of a duplicated chromosome ) , as in mitosis . but it must also separate homologous chromosomes , the similar but nonidentical chromosome pairs an organism receives from its two parents . these goals are accomplished in meiosis using a two-step division process . homologue pairs separate during a first round of cell division , called meiosis i . sister chromatids separate during a second round , called meiosis ii . since cell division occurs twice during meiosis , one starting cell can produce four gametes ( eggs or sperm ) . in each round of division , cells go through four stages : prophase , metaphase , anaphase , and telophase . meiosis i before entering meiosis i , a cell must first go through interphase . as in mitosis , the cell grows during g $ _1 $ phase , copies all of its chromosomes during s phase , and prepares for division during g $ _2 $ phase . during prophase i , differences from mitosis begin to appear . as in mitosis , the chromosomes begin to condense , but in meiosis i , they also pair up . each chromosome carefully aligns with its homologue partner so that the two match up at corresponding positions along their full length . for instance , in the image below , the letters a , b , and c represent genes found at particular spots on the chromosome , with capital and lowercase letters for different forms , or alleles , of each gene . the dna is broken at the same spot on each homologue—here , between genes b and c—and reconnected in a criss-cross pattern so that the homologues exchange part of their dna . this process , in which homologous chromosomes trade parts , is called crossing over . it 's helped along by a protein structure called the synaptonemal complex that holds the homologues together . the chromosomes would actually be positioned one on top of the other—as in the image below—throughout crossing over ; they 're only shown side-by-side in the image above so that it 's easier to see the exchange of genetic material . you can see crossovers under a microscope as chiasmata , cross-shaped structures where homologues are linked together . chiasmata keep the homologues connected to each other after the synaptonemal complex breaks down , so each homologous pair needs at least one . it 's common for multiple crossovers ( up to $ 25 $ ! ) to take place for each homologue pair $ ^1 $ . the spots where crossovers happen are more or less random , leading to the formation of new , `` remixed '' chromosomes with unique combinations of alleles . after crossing over , the spindle begins to capture chromosomes and move them towards the center of the cell ( metaphase plate ) . this may seem familiar from mitosis , but there is a twist . each chromosome attaches to microtubules from just one pole of the spindle , and the two homologues of a pair bind to microtubules from opposite poles . so , during metaphase i , homologue pairs—not individual chromosomes—line up at the metaphase plate for separation . when the homologous pairs line up at the metaphase plate , the orientation of each pair is random . for instance , in the diagram above , the pink version of the big chromosome and the purple version of the little chromosome happen to be positioned towards the same pole and go into the same cell . but the orientation could have equally well been flipped , so that both purple chromosomes went into the cell together . this allows for the formation of gametes with different sets of homologues . in anaphase i , the homologues are pulled apart and move apart to opposite ends of the cell . the sister chromatids of each chromosome , however , remain attached to one another and do n't come apart . finally , in telophase i , the chromosomes arrive at opposite poles of the cell . in some organisms , the nuclear membrane re-forms and the chromosomes decondense , although in others , this step is skipped—since cells will soon go through another round of division , meiosis ii $ ^ { 2,3 } $ . cytokinesis usually occurs at the same time as telophase i , forming two haploid daughter cells . meiosis ii cells move from meiosis i to meiosis ii without copying their dna . meiosis ii is a shorter and simpler process than meiosis i , and you may find it helpful to think of meiosis ii as “ mitosis for haploid cells . '' the cells that enter meiosis ii are the ones made in meiosis i . these cells are haploid—have just one chromosome from each homologue pair—but their chromosomes still consist of two sister chromatids . in meiosis ii , the sister chromatids separate , making haploid cells with non-duplicated chromosomes . during prophase ii , chromosomes condense and the nuclear envelope breaks down , if needed . the centrosomes move apart , the spindle forms between them , and the spindle microtubules begin to capture chromosomes . the two sister chromatids of each chromosome are captured by microtubules from opposite spindle poles . in metaphase ii , the chromosomes line up individually along the metaphase plate . in anaphase ii , the sister chromatids separate and are pulled towards opposite poles of the cell . in telophase ii , nuclear membranes form around each set of chromosomes , and the chromosomes decondense . cytokinesis splits the chromosome sets into new cells , forming the final products of meiosis : four haploid cells in which each chromosome has just one chromatid . in humans , the products of meiosis are sperm or egg cells . how meiosis `` mixes and matches '' genes the gametes produced in meiosis are all haploid , but they 're not genetically identical . for example , take a look the meiosis ii diagram above , which shows the products of meiosis for a cell with $ 2n = 4 $ chromosomes . each gamete has a unique `` sample '' of the genetic material present in the starting cell . as it turns out , there are many more potential gamete types than just the four shown in the diagram , even for a cell with with only four chromosomes . the two main reason we can get many genetically different gametes are : crossing over . the points where homologues cross over and exchange genetic material are chosen more or less at random , and they will be different in each cell that goes through meiosis . if meiosis happens many times , as in humans , crossovers will happen at many different points . random orientation of homologue pairs . the random orientation of homologue pairs in metaphase i allows for the production of gametes with many different assortments of homologous chromosomes . in a human cell , the random orientation of homologue pairs alone allows for over $ 8 $ $ \text { million } $ different types of possible gametes $ ^7 $ . when we layer crossing over on top of this , the number of genetically different gametes that you—or any other person—can make is effectively infinite . check out the video on variation in a species to learn how genetic diversity generated by meiosis ( and fertilization ) is important in evolution and helps populations survive .
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in anaphase ii , the sister chromatids separate and are pulled towards opposite poles of the cell . in telophase ii , nuclear membranes form around each set of chromosomes , and the chromosomes decondense . cytokinesis splits the chromosome sets into new cells , forming the final products of meiosis : four haploid cells in which each chromosome has just one chromatid .
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like , are they visibly shown if you were to look under a high power microscope during telophase ii ?
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introduction mitosis is used for almost all of your body ’ s cell division needs . it adds new cells during development and replaces old and worn-out cells throughout your life . the goal of mitosis is to produce daughter cells that are genetically identical to their mothers , with not a single chromosome more or less . meiosis , on the other hand , is used for just one purpose in the human body : the production of gametes—sex cells , or sperm and eggs . its goal is to make daughter cells with exactly half as many chromosomes as the starting cell . to put that another way , meiosis in humans is a division process that takes us from a diploid cell—one with two sets of chromosomes—to haploid cells—ones with a single set of chromosomes . in humans , the haploid cells made in meiosis are sperm and eggs . when a sperm and an egg join in fertilization , the two haploid sets of chromosomes form a complete diploid set : a new genome . phases of meiosis in many ways , meiosis is a lot like mitosis . the cell goes through similar stages and uses similar strategies to organize and separate chromosomes . in meiosis , however , the cell has a more complex task . it still needs to separate sister chromatids ( the two halves of a duplicated chromosome ) , as in mitosis . but it must also separate homologous chromosomes , the similar but nonidentical chromosome pairs an organism receives from its two parents . these goals are accomplished in meiosis using a two-step division process . homologue pairs separate during a first round of cell division , called meiosis i . sister chromatids separate during a second round , called meiosis ii . since cell division occurs twice during meiosis , one starting cell can produce four gametes ( eggs or sperm ) . in each round of division , cells go through four stages : prophase , metaphase , anaphase , and telophase . meiosis i before entering meiosis i , a cell must first go through interphase . as in mitosis , the cell grows during g $ _1 $ phase , copies all of its chromosomes during s phase , and prepares for division during g $ _2 $ phase . during prophase i , differences from mitosis begin to appear . as in mitosis , the chromosomes begin to condense , but in meiosis i , they also pair up . each chromosome carefully aligns with its homologue partner so that the two match up at corresponding positions along their full length . for instance , in the image below , the letters a , b , and c represent genes found at particular spots on the chromosome , with capital and lowercase letters for different forms , or alleles , of each gene . the dna is broken at the same spot on each homologue—here , between genes b and c—and reconnected in a criss-cross pattern so that the homologues exchange part of their dna . this process , in which homologous chromosomes trade parts , is called crossing over . it 's helped along by a protein structure called the synaptonemal complex that holds the homologues together . the chromosomes would actually be positioned one on top of the other—as in the image below—throughout crossing over ; they 're only shown side-by-side in the image above so that it 's easier to see the exchange of genetic material . you can see crossovers under a microscope as chiasmata , cross-shaped structures where homologues are linked together . chiasmata keep the homologues connected to each other after the synaptonemal complex breaks down , so each homologous pair needs at least one . it 's common for multiple crossovers ( up to $ 25 $ ! ) to take place for each homologue pair $ ^1 $ . the spots where crossovers happen are more or less random , leading to the formation of new , `` remixed '' chromosomes with unique combinations of alleles . after crossing over , the spindle begins to capture chromosomes and move them towards the center of the cell ( metaphase plate ) . this may seem familiar from mitosis , but there is a twist . each chromosome attaches to microtubules from just one pole of the spindle , and the two homologues of a pair bind to microtubules from opposite poles . so , during metaphase i , homologue pairs—not individual chromosomes—line up at the metaphase plate for separation . when the homologous pairs line up at the metaphase plate , the orientation of each pair is random . for instance , in the diagram above , the pink version of the big chromosome and the purple version of the little chromosome happen to be positioned towards the same pole and go into the same cell . but the orientation could have equally well been flipped , so that both purple chromosomes went into the cell together . this allows for the formation of gametes with different sets of homologues . in anaphase i , the homologues are pulled apart and move apart to opposite ends of the cell . the sister chromatids of each chromosome , however , remain attached to one another and do n't come apart . finally , in telophase i , the chromosomes arrive at opposite poles of the cell . in some organisms , the nuclear membrane re-forms and the chromosomes decondense , although in others , this step is skipped—since cells will soon go through another round of division , meiosis ii $ ^ { 2,3 } $ . cytokinesis usually occurs at the same time as telophase i , forming two haploid daughter cells . meiosis ii cells move from meiosis i to meiosis ii without copying their dna . meiosis ii is a shorter and simpler process than meiosis i , and you may find it helpful to think of meiosis ii as “ mitosis for haploid cells . '' the cells that enter meiosis ii are the ones made in meiosis i . these cells are haploid—have just one chromosome from each homologue pair—but their chromosomes still consist of two sister chromatids . in meiosis ii , the sister chromatids separate , making haploid cells with non-duplicated chromosomes . during prophase ii , chromosomes condense and the nuclear envelope breaks down , if needed . the centrosomes move apart , the spindle forms between them , and the spindle microtubules begin to capture chromosomes . the two sister chromatids of each chromosome are captured by microtubules from opposite spindle poles . in metaphase ii , the chromosomes line up individually along the metaphase plate . in anaphase ii , the sister chromatids separate and are pulled towards opposite poles of the cell . in telophase ii , nuclear membranes form around each set of chromosomes , and the chromosomes decondense . cytokinesis splits the chromosome sets into new cells , forming the final products of meiosis : four haploid cells in which each chromosome has just one chromatid . in humans , the products of meiosis are sperm or egg cells . how meiosis `` mixes and matches '' genes the gametes produced in meiosis are all haploid , but they 're not genetically identical . for example , take a look the meiosis ii diagram above , which shows the products of meiosis for a cell with $ 2n = 4 $ chromosomes . each gamete has a unique `` sample '' of the genetic material present in the starting cell . as it turns out , there are many more potential gamete types than just the four shown in the diagram , even for a cell with with only four chromosomes . the two main reason we can get many genetically different gametes are : crossing over . the points where homologues cross over and exchange genetic material are chosen more or less at random , and they will be different in each cell that goes through meiosis . if meiosis happens many times , as in humans , crossovers will happen at many different points . random orientation of homologue pairs . the random orientation of homologue pairs in metaphase i allows for the production of gametes with many different assortments of homologous chromosomes . in a human cell , the random orientation of homologue pairs alone allows for over $ 8 $ $ \text { million } $ different types of possible gametes $ ^7 $ . when we layer crossing over on top of this , the number of genetically different gametes that you—or any other person—can make is effectively infinite . check out the video on variation in a species to learn how genetic diversity generated by meiosis ( and fertilization ) is important in evolution and helps populations survive .
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cytokinesis usually occurs at the same time as telophase i , forming two haploid daughter cells . meiosis ii cells move from meiosis i to meiosis ii without copying their dna . meiosis ii is a shorter and simpler process than meiosis i , and you may find it helpful to think of meiosis ii as “ mitosis for haploid cells . ''
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why do the homologues exchange dna ( meiosis 1 , paragraphs 2-3 ) ?
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introduction mitosis is used for almost all of your body ’ s cell division needs . it adds new cells during development and replaces old and worn-out cells throughout your life . the goal of mitosis is to produce daughter cells that are genetically identical to their mothers , with not a single chromosome more or less . meiosis , on the other hand , is used for just one purpose in the human body : the production of gametes—sex cells , or sperm and eggs . its goal is to make daughter cells with exactly half as many chromosomes as the starting cell . to put that another way , meiosis in humans is a division process that takes us from a diploid cell—one with two sets of chromosomes—to haploid cells—ones with a single set of chromosomes . in humans , the haploid cells made in meiosis are sperm and eggs . when a sperm and an egg join in fertilization , the two haploid sets of chromosomes form a complete diploid set : a new genome . phases of meiosis in many ways , meiosis is a lot like mitosis . the cell goes through similar stages and uses similar strategies to organize and separate chromosomes . in meiosis , however , the cell has a more complex task . it still needs to separate sister chromatids ( the two halves of a duplicated chromosome ) , as in mitosis . but it must also separate homologous chromosomes , the similar but nonidentical chromosome pairs an organism receives from its two parents . these goals are accomplished in meiosis using a two-step division process . homologue pairs separate during a first round of cell division , called meiosis i . sister chromatids separate during a second round , called meiosis ii . since cell division occurs twice during meiosis , one starting cell can produce four gametes ( eggs or sperm ) . in each round of division , cells go through four stages : prophase , metaphase , anaphase , and telophase . meiosis i before entering meiosis i , a cell must first go through interphase . as in mitosis , the cell grows during g $ _1 $ phase , copies all of its chromosomes during s phase , and prepares for division during g $ _2 $ phase . during prophase i , differences from mitosis begin to appear . as in mitosis , the chromosomes begin to condense , but in meiosis i , they also pair up . each chromosome carefully aligns with its homologue partner so that the two match up at corresponding positions along their full length . for instance , in the image below , the letters a , b , and c represent genes found at particular spots on the chromosome , with capital and lowercase letters for different forms , or alleles , of each gene . the dna is broken at the same spot on each homologue—here , between genes b and c—and reconnected in a criss-cross pattern so that the homologues exchange part of their dna . this process , in which homologous chromosomes trade parts , is called crossing over . it 's helped along by a protein structure called the synaptonemal complex that holds the homologues together . the chromosomes would actually be positioned one on top of the other—as in the image below—throughout crossing over ; they 're only shown side-by-side in the image above so that it 's easier to see the exchange of genetic material . you can see crossovers under a microscope as chiasmata , cross-shaped structures where homologues are linked together . chiasmata keep the homologues connected to each other after the synaptonemal complex breaks down , so each homologous pair needs at least one . it 's common for multiple crossovers ( up to $ 25 $ ! ) to take place for each homologue pair $ ^1 $ . the spots where crossovers happen are more or less random , leading to the formation of new , `` remixed '' chromosomes with unique combinations of alleles . after crossing over , the spindle begins to capture chromosomes and move them towards the center of the cell ( metaphase plate ) . this may seem familiar from mitosis , but there is a twist . each chromosome attaches to microtubules from just one pole of the spindle , and the two homologues of a pair bind to microtubules from opposite poles . so , during metaphase i , homologue pairs—not individual chromosomes—line up at the metaphase plate for separation . when the homologous pairs line up at the metaphase plate , the orientation of each pair is random . for instance , in the diagram above , the pink version of the big chromosome and the purple version of the little chromosome happen to be positioned towards the same pole and go into the same cell . but the orientation could have equally well been flipped , so that both purple chromosomes went into the cell together . this allows for the formation of gametes with different sets of homologues . in anaphase i , the homologues are pulled apart and move apart to opposite ends of the cell . the sister chromatids of each chromosome , however , remain attached to one another and do n't come apart . finally , in telophase i , the chromosomes arrive at opposite poles of the cell . in some organisms , the nuclear membrane re-forms and the chromosomes decondense , although in others , this step is skipped—since cells will soon go through another round of division , meiosis ii $ ^ { 2,3 } $ . cytokinesis usually occurs at the same time as telophase i , forming two haploid daughter cells . meiosis ii cells move from meiosis i to meiosis ii without copying their dna . meiosis ii is a shorter and simpler process than meiosis i , and you may find it helpful to think of meiosis ii as “ mitosis for haploid cells . '' the cells that enter meiosis ii are the ones made in meiosis i . these cells are haploid—have just one chromosome from each homologue pair—but their chromosomes still consist of two sister chromatids . in meiosis ii , the sister chromatids separate , making haploid cells with non-duplicated chromosomes . during prophase ii , chromosomes condense and the nuclear envelope breaks down , if needed . the centrosomes move apart , the spindle forms between them , and the spindle microtubules begin to capture chromosomes . the two sister chromatids of each chromosome are captured by microtubules from opposite spindle poles . in metaphase ii , the chromosomes line up individually along the metaphase plate . in anaphase ii , the sister chromatids separate and are pulled towards opposite poles of the cell . in telophase ii , nuclear membranes form around each set of chromosomes , and the chromosomes decondense . cytokinesis splits the chromosome sets into new cells , forming the final products of meiosis : four haploid cells in which each chromosome has just one chromatid . in humans , the products of meiosis are sperm or egg cells . how meiosis `` mixes and matches '' genes the gametes produced in meiosis are all haploid , but they 're not genetically identical . for example , take a look the meiosis ii diagram above , which shows the products of meiosis for a cell with $ 2n = 4 $ chromosomes . each gamete has a unique `` sample '' of the genetic material present in the starting cell . as it turns out , there are many more potential gamete types than just the four shown in the diagram , even for a cell with with only four chromosomes . the two main reason we can get many genetically different gametes are : crossing over . the points where homologues cross over and exchange genetic material are chosen more or less at random , and they will be different in each cell that goes through meiosis . if meiosis happens many times , as in humans , crossovers will happen at many different points . random orientation of homologue pairs . the random orientation of homologue pairs in metaphase i allows for the production of gametes with many different assortments of homologous chromosomes . in a human cell , the random orientation of homologue pairs alone allows for over $ 8 $ $ \text { million } $ different types of possible gametes $ ^7 $ . when we layer crossing over on top of this , the number of genetically different gametes that you—or any other person—can make is effectively infinite . check out the video on variation in a species to learn how genetic diversity generated by meiosis ( and fertilization ) is important in evolution and helps populations survive .
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if meiosis happens many times , as in humans , crossovers will happen at many different points . random orientation of homologue pairs . the random orientation of homologue pairs in metaphase i allows for the production of gametes with many different assortments of homologous chromosomes .
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so independent assortment = random orientation of homologue pairs ?
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introduction mitosis is used for almost all of your body ’ s cell division needs . it adds new cells during development and replaces old and worn-out cells throughout your life . the goal of mitosis is to produce daughter cells that are genetically identical to their mothers , with not a single chromosome more or less . meiosis , on the other hand , is used for just one purpose in the human body : the production of gametes—sex cells , or sperm and eggs . its goal is to make daughter cells with exactly half as many chromosomes as the starting cell . to put that another way , meiosis in humans is a division process that takes us from a diploid cell—one with two sets of chromosomes—to haploid cells—ones with a single set of chromosomes . in humans , the haploid cells made in meiosis are sperm and eggs . when a sperm and an egg join in fertilization , the two haploid sets of chromosomes form a complete diploid set : a new genome . phases of meiosis in many ways , meiosis is a lot like mitosis . the cell goes through similar stages and uses similar strategies to organize and separate chromosomes . in meiosis , however , the cell has a more complex task . it still needs to separate sister chromatids ( the two halves of a duplicated chromosome ) , as in mitosis . but it must also separate homologous chromosomes , the similar but nonidentical chromosome pairs an organism receives from its two parents . these goals are accomplished in meiosis using a two-step division process . homologue pairs separate during a first round of cell division , called meiosis i . sister chromatids separate during a second round , called meiosis ii . since cell division occurs twice during meiosis , one starting cell can produce four gametes ( eggs or sperm ) . in each round of division , cells go through four stages : prophase , metaphase , anaphase , and telophase . meiosis i before entering meiosis i , a cell must first go through interphase . as in mitosis , the cell grows during g $ _1 $ phase , copies all of its chromosomes during s phase , and prepares for division during g $ _2 $ phase . during prophase i , differences from mitosis begin to appear . as in mitosis , the chromosomes begin to condense , but in meiosis i , they also pair up . each chromosome carefully aligns with its homologue partner so that the two match up at corresponding positions along their full length . for instance , in the image below , the letters a , b , and c represent genes found at particular spots on the chromosome , with capital and lowercase letters for different forms , or alleles , of each gene . the dna is broken at the same spot on each homologue—here , between genes b and c—and reconnected in a criss-cross pattern so that the homologues exchange part of their dna . this process , in which homologous chromosomes trade parts , is called crossing over . it 's helped along by a protein structure called the synaptonemal complex that holds the homologues together . the chromosomes would actually be positioned one on top of the other—as in the image below—throughout crossing over ; they 're only shown side-by-side in the image above so that it 's easier to see the exchange of genetic material . you can see crossovers under a microscope as chiasmata , cross-shaped structures where homologues are linked together . chiasmata keep the homologues connected to each other after the synaptonemal complex breaks down , so each homologous pair needs at least one . it 's common for multiple crossovers ( up to $ 25 $ ! ) to take place for each homologue pair $ ^1 $ . the spots where crossovers happen are more or less random , leading to the formation of new , `` remixed '' chromosomes with unique combinations of alleles . after crossing over , the spindle begins to capture chromosomes and move them towards the center of the cell ( metaphase plate ) . this may seem familiar from mitosis , but there is a twist . each chromosome attaches to microtubules from just one pole of the spindle , and the two homologues of a pair bind to microtubules from opposite poles . so , during metaphase i , homologue pairs—not individual chromosomes—line up at the metaphase plate for separation . when the homologous pairs line up at the metaphase plate , the orientation of each pair is random . for instance , in the diagram above , the pink version of the big chromosome and the purple version of the little chromosome happen to be positioned towards the same pole and go into the same cell . but the orientation could have equally well been flipped , so that both purple chromosomes went into the cell together . this allows for the formation of gametes with different sets of homologues . in anaphase i , the homologues are pulled apart and move apart to opposite ends of the cell . the sister chromatids of each chromosome , however , remain attached to one another and do n't come apart . finally , in telophase i , the chromosomes arrive at opposite poles of the cell . in some organisms , the nuclear membrane re-forms and the chromosomes decondense , although in others , this step is skipped—since cells will soon go through another round of division , meiosis ii $ ^ { 2,3 } $ . cytokinesis usually occurs at the same time as telophase i , forming two haploid daughter cells . meiosis ii cells move from meiosis i to meiosis ii without copying their dna . meiosis ii is a shorter and simpler process than meiosis i , and you may find it helpful to think of meiosis ii as “ mitosis for haploid cells . '' the cells that enter meiosis ii are the ones made in meiosis i . these cells are haploid—have just one chromosome from each homologue pair—but their chromosomes still consist of two sister chromatids . in meiosis ii , the sister chromatids separate , making haploid cells with non-duplicated chromosomes . during prophase ii , chromosomes condense and the nuclear envelope breaks down , if needed . the centrosomes move apart , the spindle forms between them , and the spindle microtubules begin to capture chromosomes . the two sister chromatids of each chromosome are captured by microtubules from opposite spindle poles . in metaphase ii , the chromosomes line up individually along the metaphase plate . in anaphase ii , the sister chromatids separate and are pulled towards opposite poles of the cell . in telophase ii , nuclear membranes form around each set of chromosomes , and the chromosomes decondense . cytokinesis splits the chromosome sets into new cells , forming the final products of meiosis : four haploid cells in which each chromosome has just one chromatid . in humans , the products of meiosis are sperm or egg cells . how meiosis `` mixes and matches '' genes the gametes produced in meiosis are all haploid , but they 're not genetically identical . for example , take a look the meiosis ii diagram above , which shows the products of meiosis for a cell with $ 2n = 4 $ chromosomes . each gamete has a unique `` sample '' of the genetic material present in the starting cell . as it turns out , there are many more potential gamete types than just the four shown in the diagram , even for a cell with with only four chromosomes . the two main reason we can get many genetically different gametes are : crossing over . the points where homologues cross over and exchange genetic material are chosen more or less at random , and they will be different in each cell that goes through meiosis . if meiosis happens many times , as in humans , crossovers will happen at many different points . random orientation of homologue pairs . the random orientation of homologue pairs in metaphase i allows for the production of gametes with many different assortments of homologous chromosomes . in a human cell , the random orientation of homologue pairs alone allows for over $ 8 $ $ \text { million } $ different types of possible gametes $ ^7 $ . when we layer crossing over on top of this , the number of genetically different gametes that you—or any other person—can make is effectively infinite . check out the video on variation in a species to learn how genetic diversity generated by meiosis ( and fertilization ) is important in evolution and helps populations survive .
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when a sperm and an egg join in fertilization , the two haploid sets of chromosomes form a complete diploid set : a new genome . phases of meiosis in many ways , meiosis is a lot like mitosis . the cell goes through similar stages and uses similar strategies to organize and separate chromosomes .
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so anaphase 2 on meiosis is similar to anaphase in mitosis ?
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introduction mitosis is used for almost all of your body ’ s cell division needs . it adds new cells during development and replaces old and worn-out cells throughout your life . the goal of mitosis is to produce daughter cells that are genetically identical to their mothers , with not a single chromosome more or less . meiosis , on the other hand , is used for just one purpose in the human body : the production of gametes—sex cells , or sperm and eggs . its goal is to make daughter cells with exactly half as many chromosomes as the starting cell . to put that another way , meiosis in humans is a division process that takes us from a diploid cell—one with two sets of chromosomes—to haploid cells—ones with a single set of chromosomes . in humans , the haploid cells made in meiosis are sperm and eggs . when a sperm and an egg join in fertilization , the two haploid sets of chromosomes form a complete diploid set : a new genome . phases of meiosis in many ways , meiosis is a lot like mitosis . the cell goes through similar stages and uses similar strategies to organize and separate chromosomes . in meiosis , however , the cell has a more complex task . it still needs to separate sister chromatids ( the two halves of a duplicated chromosome ) , as in mitosis . but it must also separate homologous chromosomes , the similar but nonidentical chromosome pairs an organism receives from its two parents . these goals are accomplished in meiosis using a two-step division process . homologue pairs separate during a first round of cell division , called meiosis i . sister chromatids separate during a second round , called meiosis ii . since cell division occurs twice during meiosis , one starting cell can produce four gametes ( eggs or sperm ) . in each round of division , cells go through four stages : prophase , metaphase , anaphase , and telophase . meiosis i before entering meiosis i , a cell must first go through interphase . as in mitosis , the cell grows during g $ _1 $ phase , copies all of its chromosomes during s phase , and prepares for division during g $ _2 $ phase . during prophase i , differences from mitosis begin to appear . as in mitosis , the chromosomes begin to condense , but in meiosis i , they also pair up . each chromosome carefully aligns with its homologue partner so that the two match up at corresponding positions along their full length . for instance , in the image below , the letters a , b , and c represent genes found at particular spots on the chromosome , with capital and lowercase letters for different forms , or alleles , of each gene . the dna is broken at the same spot on each homologue—here , between genes b and c—and reconnected in a criss-cross pattern so that the homologues exchange part of their dna . this process , in which homologous chromosomes trade parts , is called crossing over . it 's helped along by a protein structure called the synaptonemal complex that holds the homologues together . the chromosomes would actually be positioned one on top of the other—as in the image below—throughout crossing over ; they 're only shown side-by-side in the image above so that it 's easier to see the exchange of genetic material . you can see crossovers under a microscope as chiasmata , cross-shaped structures where homologues are linked together . chiasmata keep the homologues connected to each other after the synaptonemal complex breaks down , so each homologous pair needs at least one . it 's common for multiple crossovers ( up to $ 25 $ ! ) to take place for each homologue pair $ ^1 $ . the spots where crossovers happen are more or less random , leading to the formation of new , `` remixed '' chromosomes with unique combinations of alleles . after crossing over , the spindle begins to capture chromosomes and move them towards the center of the cell ( metaphase plate ) . this may seem familiar from mitosis , but there is a twist . each chromosome attaches to microtubules from just one pole of the spindle , and the two homologues of a pair bind to microtubules from opposite poles . so , during metaphase i , homologue pairs—not individual chromosomes—line up at the metaphase plate for separation . when the homologous pairs line up at the metaphase plate , the orientation of each pair is random . for instance , in the diagram above , the pink version of the big chromosome and the purple version of the little chromosome happen to be positioned towards the same pole and go into the same cell . but the orientation could have equally well been flipped , so that both purple chromosomes went into the cell together . this allows for the formation of gametes with different sets of homologues . in anaphase i , the homologues are pulled apart and move apart to opposite ends of the cell . the sister chromatids of each chromosome , however , remain attached to one another and do n't come apart . finally , in telophase i , the chromosomes arrive at opposite poles of the cell . in some organisms , the nuclear membrane re-forms and the chromosomes decondense , although in others , this step is skipped—since cells will soon go through another round of division , meiosis ii $ ^ { 2,3 } $ . cytokinesis usually occurs at the same time as telophase i , forming two haploid daughter cells . meiosis ii cells move from meiosis i to meiosis ii without copying their dna . meiosis ii is a shorter and simpler process than meiosis i , and you may find it helpful to think of meiosis ii as “ mitosis for haploid cells . '' the cells that enter meiosis ii are the ones made in meiosis i . these cells are haploid—have just one chromosome from each homologue pair—but their chromosomes still consist of two sister chromatids . in meiosis ii , the sister chromatids separate , making haploid cells with non-duplicated chromosomes . during prophase ii , chromosomes condense and the nuclear envelope breaks down , if needed . the centrosomes move apart , the spindle forms between them , and the spindle microtubules begin to capture chromosomes . the two sister chromatids of each chromosome are captured by microtubules from opposite spindle poles . in metaphase ii , the chromosomes line up individually along the metaphase plate . in anaphase ii , the sister chromatids separate and are pulled towards opposite poles of the cell . in telophase ii , nuclear membranes form around each set of chromosomes , and the chromosomes decondense . cytokinesis splits the chromosome sets into new cells , forming the final products of meiosis : four haploid cells in which each chromosome has just one chromatid . in humans , the products of meiosis are sperm or egg cells . how meiosis `` mixes and matches '' genes the gametes produced in meiosis are all haploid , but they 're not genetically identical . for example , take a look the meiosis ii diagram above , which shows the products of meiosis for a cell with $ 2n = 4 $ chromosomes . each gamete has a unique `` sample '' of the genetic material present in the starting cell . as it turns out , there are many more potential gamete types than just the four shown in the diagram , even for a cell with with only four chromosomes . the two main reason we can get many genetically different gametes are : crossing over . the points where homologues cross over and exchange genetic material are chosen more or less at random , and they will be different in each cell that goes through meiosis . if meiosis happens many times , as in humans , crossovers will happen at many different points . random orientation of homologue pairs . the random orientation of homologue pairs in metaphase i allows for the production of gametes with many different assortments of homologous chromosomes . in a human cell , the random orientation of homologue pairs alone allows for over $ 8 $ $ \text { million } $ different types of possible gametes $ ^7 $ . when we layer crossing over on top of this , the number of genetically different gametes that you—or any other person—can make is effectively infinite . check out the video on variation in a species to learn how genetic diversity generated by meiosis ( and fertilization ) is important in evolution and helps populations survive .
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cytokinesis usually occurs at the same time as telophase i , forming two haploid daughter cells . meiosis ii cells move from meiosis i to meiosis ii without copying their dna . meiosis ii is a shorter and simpler process than meiosis i , and you may find it helpful to think of meiosis ii as “ mitosis for haploid cells . '' the cells that enter meiosis ii are the ones made in meiosis i . these cells are haploid—have just one chromosome from each homologue pair—but their chromosomes still consist of two sister chromatids .
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what are two events that occur during meiosis to increase the genetic diversity of offspring ?
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what is mri ? magnetic resonance imaging ( mri ) is one way for healthcare professionals to look inside your body and see what is going on inside it without having to cut open your body . while there are lots of different ways to take pictures inside your body such as x-rays , computerized tomography ( ct ) scans , ultrasounds and so on , mris produce far more detailed images of the structure of a patient ’ s blood vessels , nerves , bones , and organs . how does mri work ? an mri takes pictures of places in your body that contain water , and the detail in these images comes from the ways that different tissues interfere with the electromagnetic waves coming from water molecules . the idea of water releasing electromagnetic waves may seem pretty exotic , but it turns out that most molecules do it all the time -- -the signals that they emit are just so tiny that you ’ d only notice them if you went looking for them . an mri is just a device that first excites water molecules into releasing waves , and then records the locations of those waves with high accuracy . your body is pretty much entirely made of water . blood vessels , lymph nodes , and even solid bones are soaked with water molecules , each of which contains two hydrogen atoms . at the center of each hydrogen atom sits a nucleus consisting of a single proton , which can be visualized as a tiny bar magnet with a “ north ” and “ south ” pole . just like the “ north ” and “ south ” poles of a needle on a compass tend to align with the magnetic poles of the earth , in the presence of strong magnetic fields each proton in water twists its orientation so that it aligns with the field . when health care providers first turn on the mri machine , a very strong , constant magnetic field forms that remains in place for the duration of the measurement , and this super-strong field makes all the protons try to line up with the poles of the field . this lining-up doesn ’ t mess up any of the chemical properties of the tissues , so your body continues to function normally while the doctor makes the measurement . but while this really strong constant magnetic field makes all the protons want to line up , the mri machine intentionally disrupts this field by sending a brief pulse of an additional , weaker electromagnetic field . this weaker pulse points in a different direction than the constant magnetic field , and so it disrupts the protons so that they become misaligned with the constant field . after the pulse ends the protons are left askew , but then they gradually re-align with the original constant field . you can think of it as the tiny jiggle that occurs in a compass needle when a weak magnet passes by . the compass normally points north , but the weak magnet causes the compass needle to jiggle slightly . however , unlike the needle of a normal-sized compass , the direction that the protons can align has single , well defined levels in a manner very similar to the different energy levels of electrons around an atom ’ s nucleus . just as electrons in atomic energy levels can absorb and re-emit photons when changing energy levels , the gradual realignment of the nuclear magnetic spin results in the emission of low-energy , radio frequency photons . the time and amount of re-alignment changes based on the thickness and hardness of the tissue where the water molecules are sitting , and so carefully monitoring of the arrival of re-emitted photons in the mri ’ s detectors allows the locations and shapes of different tissues to be identified . because different places in the body contain different amounts of water , mri detects the electromagnetic fields of the atoms in water molecules and uses this to determine differences in the density and shape of tissues throughout the body . where else is this effect useful ? mri uses the same physical effect as nuclear magnetic resonance ( nmr ) spectroscopy , in which the identity of an unknown compound ( like a potential new drug ) may be identified by the resonant properties ( the jiggling of protons ) of the atoms that comprise it . in fact , the only reason that the technique is called mri and not nmr is because it premiered during the cold war , during which patients were hesitant to undergo any sort of “ nuclear ” treatment ! nmr spectroscopy was originally developed to help chemists who had created strange compounds that they couldn ’ t identify . in the technique ( and just as in mri ) , an unknown sample is placed in a static magnetic field , briefly excited with radio-frequency photons ( light ) , and then allowed to re-emit those photons . nmr works because the characteristic frequency of the re-emitted photons varies very slightly based on the structure of the molecule . a proton all by itself may absorb and reemit 900 mhz photons , but when it gets near other charges ( such as in a large hydrocarbon chain ) , the magnetic field around it is gets twisted and distorted and so its resonant frequency may shift to something like 906 mhz . this means that nmr may be used to generate “ spectra ” corresponding to the amount of resonance at various frequencies , which in turn reveals details of the structure of molecules . so if a chemist looks at the nmr spectrum of her unknown sample and sees a huge peak near 906 mhz , then she knows that her sample probably has at least one hydrocarbon chain somewhere on it . the main difference between nmr spectroscopy and mri imaging is that nmr generates information ( a spectrum of light corresponding to chemical structure ) based on the frequency of emitted radiation ( which is related to the speed of the jiggling protons ) . mri instead generates information ( images of the body ) using the intensity of radiation ( the quantity of re-emitted photons ) arriving from various parts of body . protons in dense or solid structures tend to be more or less prone to misalignment when the disrupting radio waves are applied to the body ’ s tissue , resulting in a lower number of re-emitted photons coming from that region and thus a darker area in the resulting image . what methods are used to make mri work even better ? generally , using stronger stationary magnetic fields results in nicer mri images . because the water molecules in the body are warm , they are constantly jiggling around and colliding with one another . this jiggling tends to knock the alignment of protons in random directions , and so if the stationary magnetic field is too weak , these thermal forces will prevent protons from lining up , resulting in a dimmer mri image . the images get even better when the radio waves are applied multiple times , with the images from each subsequent re-emission merged together to yield a final , combined image . it ’ s like taking the same picture multiple times on your camera and blending them together in your favorite image editor to get a better exposed image . the main limitation of this method is ensuring that the patient lies still long enough that the image doesn ’ t get blurry ! sometimes there is not enough difference in structure between two tissues to see them using mri . for example , a healthcare provider may want to check out an unusual blood vessel ( such as a blood vessel with a blood clot ) , but such an image may be difficult to see because the neighboring fat and muscle tissue re-emit photons at a similar rate as the blood vessel . there just isn ’ t enough contrast between the different structures . to solve this problem , the healthcare provider may inject a contrast agent , such as gadolinium ( iii ) , into the patient ’ s bloodstream . atoms of gd ( iii ) have really unusual electrical properties that cause them to disrupt the effective magnetic field experienced by protons in the bloodstream , which in turn changes the amount of photons that the protons will absorb and emit . this causes the blood vessels to stand out from neighboring tissues in subsequent mri images . consider the following… fmri we ’ ve all seen news articles describing how different parts of the brain become active during tasks like eating or talking . these striking images of brains owe their clarity to yet another modification of mri , known as functional mri ( fmri ) . some bodily processes actually change tissues in ways that are noticeable on an mri . for example , when tissues stretch or swell , the distribution of protons in that part of the body can change enough that a detectable change will occur in the mri signal coming from that part of the body . this means that mris can be used to create movies that reveal details of events over time in a patient ’ s body . the simplest case involves imaging moving structures like the heart or lungs , which can help pinpoint abnormal valves or blood vessels that wouldn ’ t stand out in a still image . in a recently-developed fmri , information about the changing distribution of oxygen in the brain is generated based on the unique magnetic properties of blood containing oxygen versus blood without oxygen . in oxygenated blood , the electrons from the oxygen molecules tend to block applied magnetic fields , effectively screening the hydrogens in water molecules from the applied magnetic field and decreasing the rapidness with which they will align with it . deoxygenated blood does not have this screening effect , and so the protons align much faster -- -leading to more radio-frequency photons visible to the mri detector . because the changing distribution of oxygenated blood in the brain is known to correlate with neural activity , fmri can be used to image the parts of a patient ’ s brain that become active and inactive during various tasks . this makes fmri a very useful tool for neuroscientists and psychologists .
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in oxygenated blood , the electrons from the oxygen molecules tend to block applied magnetic fields , effectively screening the hydrogens in water molecules from the applied magnetic field and decreasing the rapidness with which they will align with it . deoxygenated blood does not have this screening effect , and so the protons align much faster -- -leading to more radio-frequency photons visible to the mri detector . because the changing distribution of oxygenated blood in the brain is known to correlate with neural activity , fmri can be used to image the parts of a patient ’ s brain that become active and inactive during various tasks .
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what would happen if the radio frequency is applied first without aligning the protons first using the strong external magnet ?
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what is mri ? magnetic resonance imaging ( mri ) is one way for healthcare professionals to look inside your body and see what is going on inside it without having to cut open your body . while there are lots of different ways to take pictures inside your body such as x-rays , computerized tomography ( ct ) scans , ultrasounds and so on , mris produce far more detailed images of the structure of a patient ’ s blood vessels , nerves , bones , and organs . how does mri work ? an mri takes pictures of places in your body that contain water , and the detail in these images comes from the ways that different tissues interfere with the electromagnetic waves coming from water molecules . the idea of water releasing electromagnetic waves may seem pretty exotic , but it turns out that most molecules do it all the time -- -the signals that they emit are just so tiny that you ’ d only notice them if you went looking for them . an mri is just a device that first excites water molecules into releasing waves , and then records the locations of those waves with high accuracy . your body is pretty much entirely made of water . blood vessels , lymph nodes , and even solid bones are soaked with water molecules , each of which contains two hydrogen atoms . at the center of each hydrogen atom sits a nucleus consisting of a single proton , which can be visualized as a tiny bar magnet with a “ north ” and “ south ” pole . just like the “ north ” and “ south ” poles of a needle on a compass tend to align with the magnetic poles of the earth , in the presence of strong magnetic fields each proton in water twists its orientation so that it aligns with the field . when health care providers first turn on the mri machine , a very strong , constant magnetic field forms that remains in place for the duration of the measurement , and this super-strong field makes all the protons try to line up with the poles of the field . this lining-up doesn ’ t mess up any of the chemical properties of the tissues , so your body continues to function normally while the doctor makes the measurement . but while this really strong constant magnetic field makes all the protons want to line up , the mri machine intentionally disrupts this field by sending a brief pulse of an additional , weaker electromagnetic field . this weaker pulse points in a different direction than the constant magnetic field , and so it disrupts the protons so that they become misaligned with the constant field . after the pulse ends the protons are left askew , but then they gradually re-align with the original constant field . you can think of it as the tiny jiggle that occurs in a compass needle when a weak magnet passes by . the compass normally points north , but the weak magnet causes the compass needle to jiggle slightly . however , unlike the needle of a normal-sized compass , the direction that the protons can align has single , well defined levels in a manner very similar to the different energy levels of electrons around an atom ’ s nucleus . just as electrons in atomic energy levels can absorb and re-emit photons when changing energy levels , the gradual realignment of the nuclear magnetic spin results in the emission of low-energy , radio frequency photons . the time and amount of re-alignment changes based on the thickness and hardness of the tissue where the water molecules are sitting , and so carefully monitoring of the arrival of re-emitted photons in the mri ’ s detectors allows the locations and shapes of different tissues to be identified . because different places in the body contain different amounts of water , mri detects the electromagnetic fields of the atoms in water molecules and uses this to determine differences in the density and shape of tissues throughout the body . where else is this effect useful ? mri uses the same physical effect as nuclear magnetic resonance ( nmr ) spectroscopy , in which the identity of an unknown compound ( like a potential new drug ) may be identified by the resonant properties ( the jiggling of protons ) of the atoms that comprise it . in fact , the only reason that the technique is called mri and not nmr is because it premiered during the cold war , during which patients were hesitant to undergo any sort of “ nuclear ” treatment ! nmr spectroscopy was originally developed to help chemists who had created strange compounds that they couldn ’ t identify . in the technique ( and just as in mri ) , an unknown sample is placed in a static magnetic field , briefly excited with radio-frequency photons ( light ) , and then allowed to re-emit those photons . nmr works because the characteristic frequency of the re-emitted photons varies very slightly based on the structure of the molecule . a proton all by itself may absorb and reemit 900 mhz photons , but when it gets near other charges ( such as in a large hydrocarbon chain ) , the magnetic field around it is gets twisted and distorted and so its resonant frequency may shift to something like 906 mhz . this means that nmr may be used to generate “ spectra ” corresponding to the amount of resonance at various frequencies , which in turn reveals details of the structure of molecules . so if a chemist looks at the nmr spectrum of her unknown sample and sees a huge peak near 906 mhz , then she knows that her sample probably has at least one hydrocarbon chain somewhere on it . the main difference between nmr spectroscopy and mri imaging is that nmr generates information ( a spectrum of light corresponding to chemical structure ) based on the frequency of emitted radiation ( which is related to the speed of the jiggling protons ) . mri instead generates information ( images of the body ) using the intensity of radiation ( the quantity of re-emitted photons ) arriving from various parts of body . protons in dense or solid structures tend to be more or less prone to misalignment when the disrupting radio waves are applied to the body ’ s tissue , resulting in a lower number of re-emitted photons coming from that region and thus a darker area in the resulting image . what methods are used to make mri work even better ? generally , using stronger stationary magnetic fields results in nicer mri images . because the water molecules in the body are warm , they are constantly jiggling around and colliding with one another . this jiggling tends to knock the alignment of protons in random directions , and so if the stationary magnetic field is too weak , these thermal forces will prevent protons from lining up , resulting in a dimmer mri image . the images get even better when the radio waves are applied multiple times , with the images from each subsequent re-emission merged together to yield a final , combined image . it ’ s like taking the same picture multiple times on your camera and blending them together in your favorite image editor to get a better exposed image . the main limitation of this method is ensuring that the patient lies still long enough that the image doesn ’ t get blurry ! sometimes there is not enough difference in structure between two tissues to see them using mri . for example , a healthcare provider may want to check out an unusual blood vessel ( such as a blood vessel with a blood clot ) , but such an image may be difficult to see because the neighboring fat and muscle tissue re-emit photons at a similar rate as the blood vessel . there just isn ’ t enough contrast between the different structures . to solve this problem , the healthcare provider may inject a contrast agent , such as gadolinium ( iii ) , into the patient ’ s bloodstream . atoms of gd ( iii ) have really unusual electrical properties that cause them to disrupt the effective magnetic field experienced by protons in the bloodstream , which in turn changes the amount of photons that the protons will absorb and emit . this causes the blood vessels to stand out from neighboring tissues in subsequent mri images . consider the following… fmri we ’ ve all seen news articles describing how different parts of the brain become active during tasks like eating or talking . these striking images of brains owe their clarity to yet another modification of mri , known as functional mri ( fmri ) . some bodily processes actually change tissues in ways that are noticeable on an mri . for example , when tissues stretch or swell , the distribution of protons in that part of the body can change enough that a detectable change will occur in the mri signal coming from that part of the body . this means that mris can be used to create movies that reveal details of events over time in a patient ’ s body . the simplest case involves imaging moving structures like the heart or lungs , which can help pinpoint abnormal valves or blood vessels that wouldn ’ t stand out in a still image . in a recently-developed fmri , information about the changing distribution of oxygen in the brain is generated based on the unique magnetic properties of blood containing oxygen versus blood without oxygen . in oxygenated blood , the electrons from the oxygen molecules tend to block applied magnetic fields , effectively screening the hydrogens in water molecules from the applied magnetic field and decreasing the rapidness with which they will align with it . deoxygenated blood does not have this screening effect , and so the protons align much faster -- -leading to more radio-frequency photons visible to the mri detector . because the changing distribution of oxygenated blood in the brain is known to correlate with neural activity , fmri can be used to image the parts of a patient ’ s brain that become active and inactive during various tasks . this makes fmri a very useful tool for neuroscientists and psychologists .
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your body is pretty much entirely made of water . blood vessels , lymph nodes , and even solid bones are soaked with water molecules , each of which contains two hydrogen atoms . at the center of each hydrogen atom sits a nucleus consisting of a single proton , which can be visualized as a tiny bar magnet with a “ north ” and “ south ” pole .
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how does mri specifically target only water molecules/atoms and not other molecules/atoms ?
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what is mri ? magnetic resonance imaging ( mri ) is one way for healthcare professionals to look inside your body and see what is going on inside it without having to cut open your body . while there are lots of different ways to take pictures inside your body such as x-rays , computerized tomography ( ct ) scans , ultrasounds and so on , mris produce far more detailed images of the structure of a patient ’ s blood vessels , nerves , bones , and organs . how does mri work ? an mri takes pictures of places in your body that contain water , and the detail in these images comes from the ways that different tissues interfere with the electromagnetic waves coming from water molecules . the idea of water releasing electromagnetic waves may seem pretty exotic , but it turns out that most molecules do it all the time -- -the signals that they emit are just so tiny that you ’ d only notice them if you went looking for them . an mri is just a device that first excites water molecules into releasing waves , and then records the locations of those waves with high accuracy . your body is pretty much entirely made of water . blood vessels , lymph nodes , and even solid bones are soaked with water molecules , each of which contains two hydrogen atoms . at the center of each hydrogen atom sits a nucleus consisting of a single proton , which can be visualized as a tiny bar magnet with a “ north ” and “ south ” pole . just like the “ north ” and “ south ” poles of a needle on a compass tend to align with the magnetic poles of the earth , in the presence of strong magnetic fields each proton in water twists its orientation so that it aligns with the field . when health care providers first turn on the mri machine , a very strong , constant magnetic field forms that remains in place for the duration of the measurement , and this super-strong field makes all the protons try to line up with the poles of the field . this lining-up doesn ’ t mess up any of the chemical properties of the tissues , so your body continues to function normally while the doctor makes the measurement . but while this really strong constant magnetic field makes all the protons want to line up , the mri machine intentionally disrupts this field by sending a brief pulse of an additional , weaker electromagnetic field . this weaker pulse points in a different direction than the constant magnetic field , and so it disrupts the protons so that they become misaligned with the constant field . after the pulse ends the protons are left askew , but then they gradually re-align with the original constant field . you can think of it as the tiny jiggle that occurs in a compass needle when a weak magnet passes by . the compass normally points north , but the weak magnet causes the compass needle to jiggle slightly . however , unlike the needle of a normal-sized compass , the direction that the protons can align has single , well defined levels in a manner very similar to the different energy levels of electrons around an atom ’ s nucleus . just as electrons in atomic energy levels can absorb and re-emit photons when changing energy levels , the gradual realignment of the nuclear magnetic spin results in the emission of low-energy , radio frequency photons . the time and amount of re-alignment changes based on the thickness and hardness of the tissue where the water molecules are sitting , and so carefully monitoring of the arrival of re-emitted photons in the mri ’ s detectors allows the locations and shapes of different tissues to be identified . because different places in the body contain different amounts of water , mri detects the electromagnetic fields of the atoms in water molecules and uses this to determine differences in the density and shape of tissues throughout the body . where else is this effect useful ? mri uses the same physical effect as nuclear magnetic resonance ( nmr ) spectroscopy , in which the identity of an unknown compound ( like a potential new drug ) may be identified by the resonant properties ( the jiggling of protons ) of the atoms that comprise it . in fact , the only reason that the technique is called mri and not nmr is because it premiered during the cold war , during which patients were hesitant to undergo any sort of “ nuclear ” treatment ! nmr spectroscopy was originally developed to help chemists who had created strange compounds that they couldn ’ t identify . in the technique ( and just as in mri ) , an unknown sample is placed in a static magnetic field , briefly excited with radio-frequency photons ( light ) , and then allowed to re-emit those photons . nmr works because the characteristic frequency of the re-emitted photons varies very slightly based on the structure of the molecule . a proton all by itself may absorb and reemit 900 mhz photons , but when it gets near other charges ( such as in a large hydrocarbon chain ) , the magnetic field around it is gets twisted and distorted and so its resonant frequency may shift to something like 906 mhz . this means that nmr may be used to generate “ spectra ” corresponding to the amount of resonance at various frequencies , which in turn reveals details of the structure of molecules . so if a chemist looks at the nmr spectrum of her unknown sample and sees a huge peak near 906 mhz , then she knows that her sample probably has at least one hydrocarbon chain somewhere on it . the main difference between nmr spectroscopy and mri imaging is that nmr generates information ( a spectrum of light corresponding to chemical structure ) based on the frequency of emitted radiation ( which is related to the speed of the jiggling protons ) . mri instead generates information ( images of the body ) using the intensity of radiation ( the quantity of re-emitted photons ) arriving from various parts of body . protons in dense or solid structures tend to be more or less prone to misalignment when the disrupting radio waves are applied to the body ’ s tissue , resulting in a lower number of re-emitted photons coming from that region and thus a darker area in the resulting image . what methods are used to make mri work even better ? generally , using stronger stationary magnetic fields results in nicer mri images . because the water molecules in the body are warm , they are constantly jiggling around and colliding with one another . this jiggling tends to knock the alignment of protons in random directions , and so if the stationary magnetic field is too weak , these thermal forces will prevent protons from lining up , resulting in a dimmer mri image . the images get even better when the radio waves are applied multiple times , with the images from each subsequent re-emission merged together to yield a final , combined image . it ’ s like taking the same picture multiple times on your camera and blending them together in your favorite image editor to get a better exposed image . the main limitation of this method is ensuring that the patient lies still long enough that the image doesn ’ t get blurry ! sometimes there is not enough difference in structure between two tissues to see them using mri . for example , a healthcare provider may want to check out an unusual blood vessel ( such as a blood vessel with a blood clot ) , but such an image may be difficult to see because the neighboring fat and muscle tissue re-emit photons at a similar rate as the blood vessel . there just isn ’ t enough contrast between the different structures . to solve this problem , the healthcare provider may inject a contrast agent , such as gadolinium ( iii ) , into the patient ’ s bloodstream . atoms of gd ( iii ) have really unusual electrical properties that cause them to disrupt the effective magnetic field experienced by protons in the bloodstream , which in turn changes the amount of photons that the protons will absorb and emit . this causes the blood vessels to stand out from neighboring tissues in subsequent mri images . consider the following… fmri we ’ ve all seen news articles describing how different parts of the brain become active during tasks like eating or talking . these striking images of brains owe their clarity to yet another modification of mri , known as functional mri ( fmri ) . some bodily processes actually change tissues in ways that are noticeable on an mri . for example , when tissues stretch or swell , the distribution of protons in that part of the body can change enough that a detectable change will occur in the mri signal coming from that part of the body . this means that mris can be used to create movies that reveal details of events over time in a patient ’ s body . the simplest case involves imaging moving structures like the heart or lungs , which can help pinpoint abnormal valves or blood vessels that wouldn ’ t stand out in a still image . in a recently-developed fmri , information about the changing distribution of oxygen in the brain is generated based on the unique magnetic properties of blood containing oxygen versus blood without oxygen . in oxygenated blood , the electrons from the oxygen molecules tend to block applied magnetic fields , effectively screening the hydrogens in water molecules from the applied magnetic field and decreasing the rapidness with which they will align with it . deoxygenated blood does not have this screening effect , and so the protons align much faster -- -leading to more radio-frequency photons visible to the mri detector . because the changing distribution of oxygenated blood in the brain is known to correlate with neural activity , fmri can be used to image the parts of a patient ’ s brain that become active and inactive during various tasks . this makes fmri a very useful tool for neuroscientists and psychologists .
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in a recently-developed fmri , information about the changing distribution of oxygen in the brain is generated based on the unique magnetic properties of blood containing oxygen versus blood without oxygen . in oxygenated blood , the electrons from the oxygen molecules tend to block applied magnetic fields , effectively screening the hydrogens in water molecules from the applied magnetic field and decreasing the rapidness with which they will align with it . deoxygenated blood does not have this screening effect , and so the protons align much faster -- -leading to more radio-frequency photons visible to the mri detector .
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how does this em radiation connect to an applied ( external ) b in a simple equation or 2 ( not complicated beyond scope of mcat ) ?
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what is mri ? magnetic resonance imaging ( mri ) is one way for healthcare professionals to look inside your body and see what is going on inside it without having to cut open your body . while there are lots of different ways to take pictures inside your body such as x-rays , computerized tomography ( ct ) scans , ultrasounds and so on , mris produce far more detailed images of the structure of a patient ’ s blood vessels , nerves , bones , and organs . how does mri work ? an mri takes pictures of places in your body that contain water , and the detail in these images comes from the ways that different tissues interfere with the electromagnetic waves coming from water molecules . the idea of water releasing electromagnetic waves may seem pretty exotic , but it turns out that most molecules do it all the time -- -the signals that they emit are just so tiny that you ’ d only notice them if you went looking for them . an mri is just a device that first excites water molecules into releasing waves , and then records the locations of those waves with high accuracy . your body is pretty much entirely made of water . blood vessels , lymph nodes , and even solid bones are soaked with water molecules , each of which contains two hydrogen atoms . at the center of each hydrogen atom sits a nucleus consisting of a single proton , which can be visualized as a tiny bar magnet with a “ north ” and “ south ” pole . just like the “ north ” and “ south ” poles of a needle on a compass tend to align with the magnetic poles of the earth , in the presence of strong magnetic fields each proton in water twists its orientation so that it aligns with the field . when health care providers first turn on the mri machine , a very strong , constant magnetic field forms that remains in place for the duration of the measurement , and this super-strong field makes all the protons try to line up with the poles of the field . this lining-up doesn ’ t mess up any of the chemical properties of the tissues , so your body continues to function normally while the doctor makes the measurement . but while this really strong constant magnetic field makes all the protons want to line up , the mri machine intentionally disrupts this field by sending a brief pulse of an additional , weaker electromagnetic field . this weaker pulse points in a different direction than the constant magnetic field , and so it disrupts the protons so that they become misaligned with the constant field . after the pulse ends the protons are left askew , but then they gradually re-align with the original constant field . you can think of it as the tiny jiggle that occurs in a compass needle when a weak magnet passes by . the compass normally points north , but the weak magnet causes the compass needle to jiggle slightly . however , unlike the needle of a normal-sized compass , the direction that the protons can align has single , well defined levels in a manner very similar to the different energy levels of electrons around an atom ’ s nucleus . just as electrons in atomic energy levels can absorb and re-emit photons when changing energy levels , the gradual realignment of the nuclear magnetic spin results in the emission of low-energy , radio frequency photons . the time and amount of re-alignment changes based on the thickness and hardness of the tissue where the water molecules are sitting , and so carefully monitoring of the arrival of re-emitted photons in the mri ’ s detectors allows the locations and shapes of different tissues to be identified . because different places in the body contain different amounts of water , mri detects the electromagnetic fields of the atoms in water molecules and uses this to determine differences in the density and shape of tissues throughout the body . where else is this effect useful ? mri uses the same physical effect as nuclear magnetic resonance ( nmr ) spectroscopy , in which the identity of an unknown compound ( like a potential new drug ) may be identified by the resonant properties ( the jiggling of protons ) of the atoms that comprise it . in fact , the only reason that the technique is called mri and not nmr is because it premiered during the cold war , during which patients were hesitant to undergo any sort of “ nuclear ” treatment ! nmr spectroscopy was originally developed to help chemists who had created strange compounds that they couldn ’ t identify . in the technique ( and just as in mri ) , an unknown sample is placed in a static magnetic field , briefly excited with radio-frequency photons ( light ) , and then allowed to re-emit those photons . nmr works because the characteristic frequency of the re-emitted photons varies very slightly based on the structure of the molecule . a proton all by itself may absorb and reemit 900 mhz photons , but when it gets near other charges ( such as in a large hydrocarbon chain ) , the magnetic field around it is gets twisted and distorted and so its resonant frequency may shift to something like 906 mhz . this means that nmr may be used to generate “ spectra ” corresponding to the amount of resonance at various frequencies , which in turn reveals details of the structure of molecules . so if a chemist looks at the nmr spectrum of her unknown sample and sees a huge peak near 906 mhz , then she knows that her sample probably has at least one hydrocarbon chain somewhere on it . the main difference between nmr spectroscopy and mri imaging is that nmr generates information ( a spectrum of light corresponding to chemical structure ) based on the frequency of emitted radiation ( which is related to the speed of the jiggling protons ) . mri instead generates information ( images of the body ) using the intensity of radiation ( the quantity of re-emitted photons ) arriving from various parts of body . protons in dense or solid structures tend to be more or less prone to misalignment when the disrupting radio waves are applied to the body ’ s tissue , resulting in a lower number of re-emitted photons coming from that region and thus a darker area in the resulting image . what methods are used to make mri work even better ? generally , using stronger stationary magnetic fields results in nicer mri images . because the water molecules in the body are warm , they are constantly jiggling around and colliding with one another . this jiggling tends to knock the alignment of protons in random directions , and so if the stationary magnetic field is too weak , these thermal forces will prevent protons from lining up , resulting in a dimmer mri image . the images get even better when the radio waves are applied multiple times , with the images from each subsequent re-emission merged together to yield a final , combined image . it ’ s like taking the same picture multiple times on your camera and blending them together in your favorite image editor to get a better exposed image . the main limitation of this method is ensuring that the patient lies still long enough that the image doesn ’ t get blurry ! sometimes there is not enough difference in structure between two tissues to see them using mri . for example , a healthcare provider may want to check out an unusual blood vessel ( such as a blood vessel with a blood clot ) , but such an image may be difficult to see because the neighboring fat and muscle tissue re-emit photons at a similar rate as the blood vessel . there just isn ’ t enough contrast between the different structures . to solve this problem , the healthcare provider may inject a contrast agent , such as gadolinium ( iii ) , into the patient ’ s bloodstream . atoms of gd ( iii ) have really unusual electrical properties that cause them to disrupt the effective magnetic field experienced by protons in the bloodstream , which in turn changes the amount of photons that the protons will absorb and emit . this causes the blood vessels to stand out from neighboring tissues in subsequent mri images . consider the following… fmri we ’ ve all seen news articles describing how different parts of the brain become active during tasks like eating or talking . these striking images of brains owe their clarity to yet another modification of mri , known as functional mri ( fmri ) . some bodily processes actually change tissues in ways that are noticeable on an mri . for example , when tissues stretch or swell , the distribution of protons in that part of the body can change enough that a detectable change will occur in the mri signal coming from that part of the body . this means that mris can be used to create movies that reveal details of events over time in a patient ’ s body . the simplest case involves imaging moving structures like the heart or lungs , which can help pinpoint abnormal valves or blood vessels that wouldn ’ t stand out in a still image . in a recently-developed fmri , information about the changing distribution of oxygen in the brain is generated based on the unique magnetic properties of blood containing oxygen versus blood without oxygen . in oxygenated blood , the electrons from the oxygen molecules tend to block applied magnetic fields , effectively screening the hydrogens in water molecules from the applied magnetic field and decreasing the rapidness with which they will align with it . deoxygenated blood does not have this screening effect , and so the protons align much faster -- -leading to more radio-frequency photons visible to the mri detector . because the changing distribution of oxygenated blood in the brain is known to correlate with neural activity , fmri can be used to image the parts of a patient ’ s brain that become active and inactive during various tasks . this makes fmri a very useful tool for neuroscientists and psychologists .
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protons in dense or solid structures tend to be more or less prone to misalignment when the disrupting radio waves are applied to the body ’ s tissue , resulting in a lower number of re-emitted photons coming from that region and thus a darker area in the resulting image . what methods are used to make mri work even better ? generally , using stronger stationary magnetic fields results in nicer mri images .
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can fmri be used to determine a person 's level of engagement in a task such as participation in a conversation ?
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what is mri ? magnetic resonance imaging ( mri ) is one way for healthcare professionals to look inside your body and see what is going on inside it without having to cut open your body . while there are lots of different ways to take pictures inside your body such as x-rays , computerized tomography ( ct ) scans , ultrasounds and so on , mris produce far more detailed images of the structure of a patient ’ s blood vessels , nerves , bones , and organs . how does mri work ? an mri takes pictures of places in your body that contain water , and the detail in these images comes from the ways that different tissues interfere with the electromagnetic waves coming from water molecules . the idea of water releasing electromagnetic waves may seem pretty exotic , but it turns out that most molecules do it all the time -- -the signals that they emit are just so tiny that you ’ d only notice them if you went looking for them . an mri is just a device that first excites water molecules into releasing waves , and then records the locations of those waves with high accuracy . your body is pretty much entirely made of water . blood vessels , lymph nodes , and even solid bones are soaked with water molecules , each of which contains two hydrogen atoms . at the center of each hydrogen atom sits a nucleus consisting of a single proton , which can be visualized as a tiny bar magnet with a “ north ” and “ south ” pole . just like the “ north ” and “ south ” poles of a needle on a compass tend to align with the magnetic poles of the earth , in the presence of strong magnetic fields each proton in water twists its orientation so that it aligns with the field . when health care providers first turn on the mri machine , a very strong , constant magnetic field forms that remains in place for the duration of the measurement , and this super-strong field makes all the protons try to line up with the poles of the field . this lining-up doesn ’ t mess up any of the chemical properties of the tissues , so your body continues to function normally while the doctor makes the measurement . but while this really strong constant magnetic field makes all the protons want to line up , the mri machine intentionally disrupts this field by sending a brief pulse of an additional , weaker electromagnetic field . this weaker pulse points in a different direction than the constant magnetic field , and so it disrupts the protons so that they become misaligned with the constant field . after the pulse ends the protons are left askew , but then they gradually re-align with the original constant field . you can think of it as the tiny jiggle that occurs in a compass needle when a weak magnet passes by . the compass normally points north , but the weak magnet causes the compass needle to jiggle slightly . however , unlike the needle of a normal-sized compass , the direction that the protons can align has single , well defined levels in a manner very similar to the different energy levels of electrons around an atom ’ s nucleus . just as electrons in atomic energy levels can absorb and re-emit photons when changing energy levels , the gradual realignment of the nuclear magnetic spin results in the emission of low-energy , radio frequency photons . the time and amount of re-alignment changes based on the thickness and hardness of the tissue where the water molecules are sitting , and so carefully monitoring of the arrival of re-emitted photons in the mri ’ s detectors allows the locations and shapes of different tissues to be identified . because different places in the body contain different amounts of water , mri detects the electromagnetic fields of the atoms in water molecules and uses this to determine differences in the density and shape of tissues throughout the body . where else is this effect useful ? mri uses the same physical effect as nuclear magnetic resonance ( nmr ) spectroscopy , in which the identity of an unknown compound ( like a potential new drug ) may be identified by the resonant properties ( the jiggling of protons ) of the atoms that comprise it . in fact , the only reason that the technique is called mri and not nmr is because it premiered during the cold war , during which patients were hesitant to undergo any sort of “ nuclear ” treatment ! nmr spectroscopy was originally developed to help chemists who had created strange compounds that they couldn ’ t identify . in the technique ( and just as in mri ) , an unknown sample is placed in a static magnetic field , briefly excited with radio-frequency photons ( light ) , and then allowed to re-emit those photons . nmr works because the characteristic frequency of the re-emitted photons varies very slightly based on the structure of the molecule . a proton all by itself may absorb and reemit 900 mhz photons , but when it gets near other charges ( such as in a large hydrocarbon chain ) , the magnetic field around it is gets twisted and distorted and so its resonant frequency may shift to something like 906 mhz . this means that nmr may be used to generate “ spectra ” corresponding to the amount of resonance at various frequencies , which in turn reveals details of the structure of molecules . so if a chemist looks at the nmr spectrum of her unknown sample and sees a huge peak near 906 mhz , then she knows that her sample probably has at least one hydrocarbon chain somewhere on it . the main difference between nmr spectroscopy and mri imaging is that nmr generates information ( a spectrum of light corresponding to chemical structure ) based on the frequency of emitted radiation ( which is related to the speed of the jiggling protons ) . mri instead generates information ( images of the body ) using the intensity of radiation ( the quantity of re-emitted photons ) arriving from various parts of body . protons in dense or solid structures tend to be more or less prone to misalignment when the disrupting radio waves are applied to the body ’ s tissue , resulting in a lower number of re-emitted photons coming from that region and thus a darker area in the resulting image . what methods are used to make mri work even better ? generally , using stronger stationary magnetic fields results in nicer mri images . because the water molecules in the body are warm , they are constantly jiggling around and colliding with one another . this jiggling tends to knock the alignment of protons in random directions , and so if the stationary magnetic field is too weak , these thermal forces will prevent protons from lining up , resulting in a dimmer mri image . the images get even better when the radio waves are applied multiple times , with the images from each subsequent re-emission merged together to yield a final , combined image . it ’ s like taking the same picture multiple times on your camera and blending them together in your favorite image editor to get a better exposed image . the main limitation of this method is ensuring that the patient lies still long enough that the image doesn ’ t get blurry ! sometimes there is not enough difference in structure between two tissues to see them using mri . for example , a healthcare provider may want to check out an unusual blood vessel ( such as a blood vessel with a blood clot ) , but such an image may be difficult to see because the neighboring fat and muscle tissue re-emit photons at a similar rate as the blood vessel . there just isn ’ t enough contrast between the different structures . to solve this problem , the healthcare provider may inject a contrast agent , such as gadolinium ( iii ) , into the patient ’ s bloodstream . atoms of gd ( iii ) have really unusual electrical properties that cause them to disrupt the effective magnetic field experienced by protons in the bloodstream , which in turn changes the amount of photons that the protons will absorb and emit . this causes the blood vessels to stand out from neighboring tissues in subsequent mri images . consider the following… fmri we ’ ve all seen news articles describing how different parts of the brain become active during tasks like eating or talking . these striking images of brains owe their clarity to yet another modification of mri , known as functional mri ( fmri ) . some bodily processes actually change tissues in ways that are noticeable on an mri . for example , when tissues stretch or swell , the distribution of protons in that part of the body can change enough that a detectable change will occur in the mri signal coming from that part of the body . this means that mris can be used to create movies that reveal details of events over time in a patient ’ s body . the simplest case involves imaging moving structures like the heart or lungs , which can help pinpoint abnormal valves or blood vessels that wouldn ’ t stand out in a still image . in a recently-developed fmri , information about the changing distribution of oxygen in the brain is generated based on the unique magnetic properties of blood containing oxygen versus blood without oxygen . in oxygenated blood , the electrons from the oxygen molecules tend to block applied magnetic fields , effectively screening the hydrogens in water molecules from the applied magnetic field and decreasing the rapidness with which they will align with it . deoxygenated blood does not have this screening effect , and so the protons align much faster -- -leading to more radio-frequency photons visible to the mri detector . because the changing distribution of oxygenated blood in the brain is known to correlate with neural activity , fmri can be used to image the parts of a patient ’ s brain that become active and inactive during various tasks . this makes fmri a very useful tool for neuroscientists and psychologists .
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because the changing distribution of oxygenated blood in the brain is known to correlate with neural activity , fmri can be used to image the parts of a patient ’ s brain that become active and inactive during various tasks . this makes fmri a very useful tool for neuroscientists and psychologists .
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what is the difference between an event-related fmri design and a block fmri design ?
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what are z-scores ? a z-score measures exactly how many standard deviations above or below the mean a data point is . here 's the formula for calculating a z-score : $ z=\dfrac { \text { data point } -\text { mean } } { \text { standard deviation } } $ here 's the same formula written with symbols : $ z=\dfrac { x-\mu } { \sigma } $ here are some important facts about z-scores : a positive z-score says the data point is above average . a negative z-score says the data point is below average . a z-score close to $ 0 $ says the data point is close to average . a data point can be considered unusual if its z-score is above $ 3 $ or below $ -3 $ . want to learn more about z-scores ? check out this video . example 1 the grades on a history midterm at almond have a mean of $ \mu = 85 $ and a standard deviation of $ \sigma = 2 $ . michael scored $ 86 $ on the exam . find the z-score for michael 's exam grade . $ \begin { align } z & amp ; =\dfrac { \text { his grade } -\text { mean grade } } { \text { standard deviation } } \ \ z & amp ; =\dfrac { 86-85 } { 2 } \ \ z & amp ; =\dfrac { 1 } { 2 } =0.5\end { align } $ michael 's z-score is $ 0.5 $ . his grade was half of a standard deviation above the mean . example 2 the grades on a geometry midterm at almond have a mean of $ \mu = 82 $ and a standard deviation of $ \sigma = 4 $ . michael scored $ 74 $ on the exam . find the z-score for michael 's exam grade . $ \begin { align } z & amp ; =\dfrac { \text { his grade } -\text { mean grade } } { \text { standard deviation } } \ \ z & amp ; =\dfrac { 74-82 } { 4 } \ \ z & amp ; =\dfrac { -8 } { 4 } =-2\end { align } $ michael 's z-score is $ -2 $ . his grade was two standard deviations below the mean . practice problems want to practice more problems like these ? check out this exercise .
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what are z-scores ? a z-score measures exactly how many standard deviations above or below the mean a data point is . here 's the formula for calculating a z-score : $ z=\dfrac { \text { data point } -\text { mean } } { \text { standard deviation } } $ here 's the same formula written with symbols : $ z=\dfrac { x-\mu } { \sigma } $ here are some important facts about z-scores : a positive z-score says the data point is above average . a negative z-score says the data point is below average . a z-score close to $ 0 $ says the data point is close to average . a data point can be considered unusual if its z-score is above $ 3 $ or below $ -3 $ . want to learn more about z-scores ? check out this video .
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how do i calculate the probability of a z-score ?
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what are z-scores ? a z-score measures exactly how many standard deviations above or below the mean a data point is . here 's the formula for calculating a z-score : $ z=\dfrac { \text { data point } -\text { mean } } { \text { standard deviation } } $ here 's the same formula written with symbols : $ z=\dfrac { x-\mu } { \sigma } $ here are some important facts about z-scores : a positive z-score says the data point is above average . a negative z-score says the data point is below average . a z-score close to $ 0 $ says the data point is close to average . a data point can be considered unusual if its z-score is above $ 3 $ or below $ -3 $ . want to learn more about z-scores ? check out this video . example 1 the grades on a history midterm at almond have a mean of $ \mu = 85 $ and a standard deviation of $ \sigma = 2 $ . michael scored $ 86 $ on the exam . find the z-score for michael 's exam grade . $ \begin { align } z & amp ; =\dfrac { \text { his grade } -\text { mean grade } } { \text { standard deviation } } \ \ z & amp ; =\dfrac { 86-85 } { 2 } \ \ z & amp ; =\dfrac { 1 } { 2 } =0.5\end { align } $ michael 's z-score is $ 0.5 $ . his grade was half of a standard deviation above the mean . example 2 the grades on a geometry midterm at almond have a mean of $ \mu = 82 $ and a standard deviation of $ \sigma = 4 $ . michael scored $ 74 $ on the exam . find the z-score for michael 's exam grade . $ \begin { align } z & amp ; =\dfrac { \text { his grade } -\text { mean grade } } { \text { standard deviation } } \ \ z & amp ; =\dfrac { 74-82 } { 4 } \ \ z & amp ; =\dfrac { -8 } { 4 } =-2\end { align } $ michael 's z-score is $ -2 $ . his grade was two standard deviations below the mean . practice problems want to practice more problems like these ? check out this exercise .
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what are z-scores ? a z-score measures exactly how many standard deviations above or below the mean a data point is .
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how do you calculate the mean when you are only given the z-scores ?
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what are z-scores ? a z-score measures exactly how many standard deviations above or below the mean a data point is . here 's the formula for calculating a z-score : $ z=\dfrac { \text { data point } -\text { mean } } { \text { standard deviation } } $ here 's the same formula written with symbols : $ z=\dfrac { x-\mu } { \sigma } $ here are some important facts about z-scores : a positive z-score says the data point is above average . a negative z-score says the data point is below average . a z-score close to $ 0 $ says the data point is close to average . a data point can be considered unusual if its z-score is above $ 3 $ or below $ -3 $ . want to learn more about z-scores ? check out this video . example 1 the grades on a history midterm at almond have a mean of $ \mu = 85 $ and a standard deviation of $ \sigma = 2 $ . michael scored $ 86 $ on the exam . find the z-score for michael 's exam grade . $ \begin { align } z & amp ; =\dfrac { \text { his grade } -\text { mean grade } } { \text { standard deviation } } \ \ z & amp ; =\dfrac { 86-85 } { 2 } \ \ z & amp ; =\dfrac { 1 } { 2 } =0.5\end { align } $ michael 's z-score is $ 0.5 $ . his grade was half of a standard deviation above the mean . example 2 the grades on a geometry midterm at almond have a mean of $ \mu = 82 $ and a standard deviation of $ \sigma = 4 $ . michael scored $ 74 $ on the exam . find the z-score for michael 's exam grade . $ \begin { align } z & amp ; =\dfrac { \text { his grade } -\text { mean grade } } { \text { standard deviation } } \ \ z & amp ; =\dfrac { 74-82 } { 4 } \ \ z & amp ; =\dfrac { -8 } { 4 } =-2\end { align } $ michael 's z-score is $ -2 $ . his grade was two standard deviations below the mean . practice problems want to practice more problems like these ? check out this exercise .
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what are z-scores ? a z-score measures exactly how many standard deviations above or below the mean a data point is . here 's the formula for calculating a z-score : $ z=\dfrac { \text { data point } -\text { mean } } { \text { standard deviation } } $ here 's the same formula written with symbols : $ z=\dfrac { x-\mu } { \sigma } $ here are some important facts about z-scores : a positive z-score says the data point is above average . a negative z-score says the data point is below average .
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how do you find the data when you have the mean , the z-score , and the standard deviation ?
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what are z-scores ? a z-score measures exactly how many standard deviations above or below the mean a data point is . here 's the formula for calculating a z-score : $ z=\dfrac { \text { data point } -\text { mean } } { \text { standard deviation } } $ here 's the same formula written with symbols : $ z=\dfrac { x-\mu } { \sigma } $ here are some important facts about z-scores : a positive z-score says the data point is above average . a negative z-score says the data point is below average . a z-score close to $ 0 $ says the data point is close to average . a data point can be considered unusual if its z-score is above $ 3 $ or below $ -3 $ . want to learn more about z-scores ? check out this video . example 1 the grades on a history midterm at almond have a mean of $ \mu = 85 $ and a standard deviation of $ \sigma = 2 $ . michael scored $ 86 $ on the exam . find the z-score for michael 's exam grade . $ \begin { align } z & amp ; =\dfrac { \text { his grade } -\text { mean grade } } { \text { standard deviation } } \ \ z & amp ; =\dfrac { 86-85 } { 2 } \ \ z & amp ; =\dfrac { 1 } { 2 } =0.5\end { align } $ michael 's z-score is $ 0.5 $ . his grade was half of a standard deviation above the mean . example 2 the grades on a geometry midterm at almond have a mean of $ \mu = 82 $ and a standard deviation of $ \sigma = 4 $ . michael scored $ 74 $ on the exam . find the z-score for michael 's exam grade . $ \begin { align } z & amp ; =\dfrac { \text { his grade } -\text { mean grade } } { \text { standard deviation } } \ \ z & amp ; =\dfrac { 74-82 } { 4 } \ \ z & amp ; =\dfrac { -8 } { 4 } =-2\end { align } $ michael 's z-score is $ -2 $ . his grade was two standard deviations below the mean . practice problems want to practice more problems like these ? check out this exercise .
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what are z-scores ? a z-score measures exactly how many standard deviations above or below the mean a data point is .
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a ) what proportion of such biostatisticians will make more than $ 80,000 ?
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what are z-scores ? a z-score measures exactly how many standard deviations above or below the mean a data point is . here 's the formula for calculating a z-score : $ z=\dfrac { \text { data point } -\text { mean } } { \text { standard deviation } } $ here 's the same formula written with symbols : $ z=\dfrac { x-\mu } { \sigma } $ here are some important facts about z-scores : a positive z-score says the data point is above average . a negative z-score says the data point is below average . a z-score close to $ 0 $ says the data point is close to average . a data point can be considered unusual if its z-score is above $ 3 $ or below $ -3 $ . want to learn more about z-scores ? check out this video . example 1 the grades on a history midterm at almond have a mean of $ \mu = 85 $ and a standard deviation of $ \sigma = 2 $ . michael scored $ 86 $ on the exam . find the z-score for michael 's exam grade . $ \begin { align } z & amp ; =\dfrac { \text { his grade } -\text { mean grade } } { \text { standard deviation } } \ \ z & amp ; =\dfrac { 86-85 } { 2 } \ \ z & amp ; =\dfrac { 1 } { 2 } =0.5\end { align } $ michael 's z-score is $ 0.5 $ . his grade was half of a standard deviation above the mean . example 2 the grades on a geometry midterm at almond have a mean of $ \mu = 82 $ and a standard deviation of $ \sigma = 4 $ . michael scored $ 74 $ on the exam . find the z-score for michael 's exam grade . $ \begin { align } z & amp ; =\dfrac { \text { his grade } -\text { mean grade } } { \text { standard deviation } } \ \ z & amp ; =\dfrac { 74-82 } { 4 } \ \ z & amp ; =\dfrac { -8 } { 4 } =-2\end { align } $ michael 's z-score is $ -2 $ . his grade was two standard deviations below the mean . practice problems want to practice more problems like these ? check out this exercise .
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what are z-scores ? a z-score measures exactly how many standard deviations above or below the mean a data point is .
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b ) what proportion of such biostatisticians will make less than $ 70,000 ?
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what are z-scores ? a z-score measures exactly how many standard deviations above or below the mean a data point is . here 's the formula for calculating a z-score : $ z=\dfrac { \text { data point } -\text { mean } } { \text { standard deviation } } $ here 's the same formula written with symbols : $ z=\dfrac { x-\mu } { \sigma } $ here are some important facts about z-scores : a positive z-score says the data point is above average . a negative z-score says the data point is below average . a z-score close to $ 0 $ says the data point is close to average . a data point can be considered unusual if its z-score is above $ 3 $ or below $ -3 $ . want to learn more about z-scores ? check out this video . example 1 the grades on a history midterm at almond have a mean of $ \mu = 85 $ and a standard deviation of $ \sigma = 2 $ . michael scored $ 86 $ on the exam . find the z-score for michael 's exam grade . $ \begin { align } z & amp ; =\dfrac { \text { his grade } -\text { mean grade } } { \text { standard deviation } } \ \ z & amp ; =\dfrac { 86-85 } { 2 } \ \ z & amp ; =\dfrac { 1 } { 2 } =0.5\end { align } $ michael 's z-score is $ 0.5 $ . his grade was half of a standard deviation above the mean . example 2 the grades on a geometry midterm at almond have a mean of $ \mu = 82 $ and a standard deviation of $ \sigma = 4 $ . michael scored $ 74 $ on the exam . find the z-score for michael 's exam grade . $ \begin { align } z & amp ; =\dfrac { \text { his grade } -\text { mean grade } } { \text { standard deviation } } \ \ z & amp ; =\dfrac { 74-82 } { 4 } \ \ z & amp ; =\dfrac { -8 } { 4 } =-2\end { align } $ michael 's z-score is $ -2 $ . his grade was two standard deviations below the mean . practice problems want to practice more problems like these ? check out this exercise .
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what are z-scores ? a z-score measures exactly how many standard deviations above or below the mean a data point is .
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if we made the average of all z-scores of a group , would that give 0 ?
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what are z-scores ? a z-score measures exactly how many standard deviations above or below the mean a data point is . here 's the formula for calculating a z-score : $ z=\dfrac { \text { data point } -\text { mean } } { \text { standard deviation } } $ here 's the same formula written with symbols : $ z=\dfrac { x-\mu } { \sigma } $ here are some important facts about z-scores : a positive z-score says the data point is above average . a negative z-score says the data point is below average . a z-score close to $ 0 $ says the data point is close to average . a data point can be considered unusual if its z-score is above $ 3 $ or below $ -3 $ . want to learn more about z-scores ? check out this video . example 1 the grades on a history midterm at almond have a mean of $ \mu = 85 $ and a standard deviation of $ \sigma = 2 $ . michael scored $ 86 $ on the exam . find the z-score for michael 's exam grade . $ \begin { align } z & amp ; =\dfrac { \text { his grade } -\text { mean grade } } { \text { standard deviation } } \ \ z & amp ; =\dfrac { 86-85 } { 2 } \ \ z & amp ; =\dfrac { 1 } { 2 } =0.5\end { align } $ michael 's z-score is $ 0.5 $ . his grade was half of a standard deviation above the mean . example 2 the grades on a geometry midterm at almond have a mean of $ \mu = 82 $ and a standard deviation of $ \sigma = 4 $ . michael scored $ 74 $ on the exam . find the z-score for michael 's exam grade . $ \begin { align } z & amp ; =\dfrac { \text { his grade } -\text { mean grade } } { \text { standard deviation } } \ \ z & amp ; =\dfrac { 74-82 } { 4 } \ \ z & amp ; =\dfrac { -8 } { 4 } =-2\end { align } $ michael 's z-score is $ -2 $ . his grade was two standard deviations below the mean . practice problems want to practice more problems like these ? check out this exercise .
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a z-score close to $ 0 $ says the data point is close to average . a data point can be considered unusual if its z-score is above $ 3 $ or below $ -3 $ . want to learn more about z-scores ?
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hello everybody , i want to ask , how to calculate that has z-score is more than 3 or -3 ?
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what are z-scores ? a z-score measures exactly how many standard deviations above or below the mean a data point is . here 's the formula for calculating a z-score : $ z=\dfrac { \text { data point } -\text { mean } } { \text { standard deviation } } $ here 's the same formula written with symbols : $ z=\dfrac { x-\mu } { \sigma } $ here are some important facts about z-scores : a positive z-score says the data point is above average . a negative z-score says the data point is below average . a z-score close to $ 0 $ says the data point is close to average . a data point can be considered unusual if its z-score is above $ 3 $ or below $ -3 $ . want to learn more about z-scores ? check out this video . example 1 the grades on a history midterm at almond have a mean of $ \mu = 85 $ and a standard deviation of $ \sigma = 2 $ . michael scored $ 86 $ on the exam . find the z-score for michael 's exam grade . $ \begin { align } z & amp ; =\dfrac { \text { his grade } -\text { mean grade } } { \text { standard deviation } } \ \ z & amp ; =\dfrac { 86-85 } { 2 } \ \ z & amp ; =\dfrac { 1 } { 2 } =0.5\end { align } $ michael 's z-score is $ 0.5 $ . his grade was half of a standard deviation above the mean . example 2 the grades on a geometry midterm at almond have a mean of $ \mu = 82 $ and a standard deviation of $ \sigma = 4 $ . michael scored $ 74 $ on the exam . find the z-score for michael 's exam grade . $ \begin { align } z & amp ; =\dfrac { \text { his grade } -\text { mean grade } } { \text { standard deviation } } \ \ z & amp ; =\dfrac { 74-82 } { 4 } \ \ z & amp ; =\dfrac { -8 } { 4 } =-2\end { align } $ michael 's z-score is $ -2 $ . his grade was two standard deviations below the mean . practice problems want to practice more problems like these ? check out this exercise .
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find the z-score for michael 's exam grade . $ \begin { align } z & amp ; =\dfrac { \text { his grade } -\text { mean grade } } { \text { standard deviation } } \ \ z & amp ; =\dfrac { 86-85 } { 2 } \ \ z & amp ; =\dfrac { 1 } { 2 } =0.5\end { align } $ michael 's z-score is $ 0.5 $ . his grade was half of a standard deviation above the mean . example 2 the grades on a geometry midterm at almond have a mean of $ \mu = 82 $ and a standard deviation of $ \sigma = 4 $ . michael scored $ 74 $ on the exam .
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if the results form a normal distribution , how many students would be expected to score a result between 1 and 2 standard deviation above the mean ?
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what are z-scores ? a z-score measures exactly how many standard deviations above or below the mean a data point is . here 's the formula for calculating a z-score : $ z=\dfrac { \text { data point } -\text { mean } } { \text { standard deviation } } $ here 's the same formula written with symbols : $ z=\dfrac { x-\mu } { \sigma } $ here are some important facts about z-scores : a positive z-score says the data point is above average . a negative z-score says the data point is below average . a z-score close to $ 0 $ says the data point is close to average . a data point can be considered unusual if its z-score is above $ 3 $ or below $ -3 $ . want to learn more about z-scores ? check out this video . example 1 the grades on a history midterm at almond have a mean of $ \mu = 85 $ and a standard deviation of $ \sigma = 2 $ . michael scored $ 86 $ on the exam . find the z-score for michael 's exam grade . $ \begin { align } z & amp ; =\dfrac { \text { his grade } -\text { mean grade } } { \text { standard deviation } } \ \ z & amp ; =\dfrac { 86-85 } { 2 } \ \ z & amp ; =\dfrac { 1 } { 2 } =0.5\end { align } $ michael 's z-score is $ 0.5 $ . his grade was half of a standard deviation above the mean . example 2 the grades on a geometry midterm at almond have a mean of $ \mu = 82 $ and a standard deviation of $ \sigma = 4 $ . michael scored $ 74 $ on the exam . find the z-score for michael 's exam grade . $ \begin { align } z & amp ; =\dfrac { \text { his grade } -\text { mean grade } } { \text { standard deviation } } \ \ z & amp ; =\dfrac { 74-82 } { 4 } \ \ z & amp ; =\dfrac { -8 } { 4 } =-2\end { align } $ michael 's z-score is $ -2 $ . his grade was two standard deviations below the mean . practice problems want to practice more problems like these ? check out this exercise .
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what are z-scores ? a z-score measures exactly how many standard deviations above or below the mean a data point is .
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-68 % of the scores have z-scores between -1 and 1 -95 % of the scores have z-scores between -2 and 2 - 99.7 % of the scores have z-scores between -3 and 3 a ) 8100 b ) 16 200 c ) 20 400 d ) 28 500 can you explain it ?
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what are the three components of armor found here ? the main element is a helmet ( kabuto ) with a two-lobed projection attached at the back of the bowl and ornamental ridges fanning out from the crest . suspended at the back and sides is a six-tiered neck guard . completing the assembly is a red half-mask—complete with wrinkles , teeth , and bristling facial hair—rising above a four-tiered throat guard . who might have worn this helmet ? high-ranking samurai from the 1500s to the 1800s wore flamboyant helmets designed and produced according to their specifications . what is the purpose of such a helmet ? beyond the obvious need for defense , the creation of such equipment emerged from the samurai ’ s desire to stand out on the battlefield . a helmet ’ s distinctive features , especially the shaped attachments that appear on many examples , identified the wearer and ensured that his actions were visible to all . visual symbols of leadership , these helmets set apart those who were morally accountable for battlefield decisions , according to the samurai code . they could also be used to identify warriors after death , and were part of the military regalia in which they were buried . some elements , such as this mask , were surely meant to intimidate opponents : the red face , aggressive expression and facial hair would create a frightening impression . red was a color thought to ward off evil , and made the warrior resemble one of a host of powerful , red-faced deities familiar in japanese lore . how was this type of armor made ? the helmet bowl is made of iron , but the projections at the top appear to have been built up first with leather then with laminated paper coated with layers of dark-brown lacquer ( necessary for waterproofing ) . the back of the helmet was finished with red lacquer , and the front was coated to resemble oxidized iron . the neck guard on this helmet consists of six horizontal iron bands , coated with lacquer and laced together with turquoise-colored silk cords . the throat guard , fastened at the lower edge of the face cover , is similarly constructed . iron was also used for the mask , though the nose was formed separately and secured with pins , allowing for removal . the high level of craftsmanship and expensive materials used here are indicative of the samurai ’ s wealth and status ; ordinary warriors would not be able to afford such protection .
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they could also be used to identify warriors after death , and were part of the military regalia in which they were buried . some elements , such as this mask , were surely meant to intimidate opponents : the red face , aggressive expression and facial hair would create a frightening impression . red was a color thought to ward off evil , and made the warrior resemble one of a host of powerful , red-faced deities familiar in japanese lore . how was this type of armor made ?
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what was the red mask called by the japanese samurai ?
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what are the three components of armor found here ? the main element is a helmet ( kabuto ) with a two-lobed projection attached at the back of the bowl and ornamental ridges fanning out from the crest . suspended at the back and sides is a six-tiered neck guard . completing the assembly is a red half-mask—complete with wrinkles , teeth , and bristling facial hair—rising above a four-tiered throat guard . who might have worn this helmet ? high-ranking samurai from the 1500s to the 1800s wore flamboyant helmets designed and produced according to their specifications . what is the purpose of such a helmet ? beyond the obvious need for defense , the creation of such equipment emerged from the samurai ’ s desire to stand out on the battlefield . a helmet ’ s distinctive features , especially the shaped attachments that appear on many examples , identified the wearer and ensured that his actions were visible to all . visual symbols of leadership , these helmets set apart those who were morally accountable for battlefield decisions , according to the samurai code . they could also be used to identify warriors after death , and were part of the military regalia in which they were buried . some elements , such as this mask , were surely meant to intimidate opponents : the red face , aggressive expression and facial hair would create a frightening impression . red was a color thought to ward off evil , and made the warrior resemble one of a host of powerful , red-faced deities familiar in japanese lore . how was this type of armor made ? the helmet bowl is made of iron , but the projections at the top appear to have been built up first with leather then with laminated paper coated with layers of dark-brown lacquer ( necessary for waterproofing ) . the back of the helmet was finished with red lacquer , and the front was coated to resemble oxidized iron . the neck guard on this helmet consists of six horizontal iron bands , coated with lacquer and laced together with turquoise-colored silk cords . the throat guard , fastened at the lower edge of the face cover , is similarly constructed . iron was also used for the mask , though the nose was formed separately and secured with pins , allowing for removal . the high level of craftsmanship and expensive materials used here are indicative of the samurai ’ s wealth and status ; ordinary warriors would not be able to afford such protection .
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a helmet ’ s distinctive features , especially the shaped attachments that appear on many examples , identified the wearer and ensured that his actions were visible to all . visual symbols of leadership , these helmets set apart those who were morally accountable for battlefield decisions , according to the samurai code . they could also be used to identify warriors after death , and were part of the military regalia in which they were buried .
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how much did these helmets typically weigh ?
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what are the three components of armor found here ? the main element is a helmet ( kabuto ) with a two-lobed projection attached at the back of the bowl and ornamental ridges fanning out from the crest . suspended at the back and sides is a six-tiered neck guard . completing the assembly is a red half-mask—complete with wrinkles , teeth , and bristling facial hair—rising above a four-tiered throat guard . who might have worn this helmet ? high-ranking samurai from the 1500s to the 1800s wore flamboyant helmets designed and produced according to their specifications . what is the purpose of such a helmet ? beyond the obvious need for defense , the creation of such equipment emerged from the samurai ’ s desire to stand out on the battlefield . a helmet ’ s distinctive features , especially the shaped attachments that appear on many examples , identified the wearer and ensured that his actions were visible to all . visual symbols of leadership , these helmets set apart those who were morally accountable for battlefield decisions , according to the samurai code . they could also be used to identify warriors after death , and were part of the military regalia in which they were buried . some elements , such as this mask , were surely meant to intimidate opponents : the red face , aggressive expression and facial hair would create a frightening impression . red was a color thought to ward off evil , and made the warrior resemble one of a host of powerful , red-faced deities familiar in japanese lore . how was this type of armor made ? the helmet bowl is made of iron , but the projections at the top appear to have been built up first with leather then with laminated paper coated with layers of dark-brown lacquer ( necessary for waterproofing ) . the back of the helmet was finished with red lacquer , and the front was coated to resemble oxidized iron . the neck guard on this helmet consists of six horizontal iron bands , coated with lacquer and laced together with turquoise-colored silk cords . the throat guard , fastened at the lower edge of the face cover , is similarly constructed . iron was also used for the mask , though the nose was formed separately and secured with pins , allowing for removal . the high level of craftsmanship and expensive materials used here are indicative of the samurai ’ s wealth and status ; ordinary warriors would not be able to afford such protection .
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some elements , such as this mask , were surely meant to intimidate opponents : the red face , aggressive expression and facial hair would create a frightening impression . red was a color thought to ward off evil , and made the warrior resemble one of a host of powerful , red-faced deities familiar in japanese lore . how was this type of armor made ?
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who were the `` red faced deities '' that the mask was supposed to resemble ?
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what are the three components of armor found here ? the main element is a helmet ( kabuto ) with a two-lobed projection attached at the back of the bowl and ornamental ridges fanning out from the crest . suspended at the back and sides is a six-tiered neck guard . completing the assembly is a red half-mask—complete with wrinkles , teeth , and bristling facial hair—rising above a four-tiered throat guard . who might have worn this helmet ? high-ranking samurai from the 1500s to the 1800s wore flamboyant helmets designed and produced according to their specifications . what is the purpose of such a helmet ? beyond the obvious need for defense , the creation of such equipment emerged from the samurai ’ s desire to stand out on the battlefield . a helmet ’ s distinctive features , especially the shaped attachments that appear on many examples , identified the wearer and ensured that his actions were visible to all . visual symbols of leadership , these helmets set apart those who were morally accountable for battlefield decisions , according to the samurai code . they could also be used to identify warriors after death , and were part of the military regalia in which they were buried . some elements , such as this mask , were surely meant to intimidate opponents : the red face , aggressive expression and facial hair would create a frightening impression . red was a color thought to ward off evil , and made the warrior resemble one of a host of powerful , red-faced deities familiar in japanese lore . how was this type of armor made ? the helmet bowl is made of iron , but the projections at the top appear to have been built up first with leather then with laminated paper coated with layers of dark-brown lacquer ( necessary for waterproofing ) . the back of the helmet was finished with red lacquer , and the front was coated to resemble oxidized iron . the neck guard on this helmet consists of six horizontal iron bands , coated with lacquer and laced together with turquoise-colored silk cords . the throat guard , fastened at the lower edge of the face cover , is similarly constructed . iron was also used for the mask , though the nose was formed separately and secured with pins , allowing for removal . the high level of craftsmanship and expensive materials used here are indicative of the samurai ’ s wealth and status ; ordinary warriors would not be able to afford such protection .
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suspended at the back and sides is a six-tiered neck guard . completing the assembly is a red half-mask—complete with wrinkles , teeth , and bristling facial hair—rising above a four-tiered throat guard . who might have worn this helmet ?
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why does the mask have a fake mustache ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century .
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when the speed decreases , does the light has less energy ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains .
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so do different kinds of lightbulbs give off different spectrums ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) .
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where do we find a photon in an atom ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light .
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how do you sole for wavelength ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light .
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what is a wave exactly ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ .
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should n't amplitude , in some way , be directly related to energy ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ .
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from where photon is emmited or absorbed ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ?
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: if you take the `` frequency of a light wave '' and multiply it by `` 6.626*10tothe-34 '' you get the frequency of a photon of that light wave ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low .
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why do things travel in waves and not in a straight line ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low .
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so why do electrons make waves ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light .
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what is that in the sound wave that makes that to need some medium to pass through and what is that in electro magnetic wave that does n't need any medium like sound wave ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter .
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when we say that a wave oscillates , are the photons oscillating or something else ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter .
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if photons are oscillating , then are they oscillating in the electric field or magnetic field ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties .
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what is the problem if we try to explain black body radiation by using wave theory of light ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light .
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does black body radiation have different colours or can we see it ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules .
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1. why can we say that light is a particle ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed .
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why is it that photons cant transfer energy which is less than the quantised number ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve .
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how was quantization able to solve the uv catastrophe ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true .
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so , energy ca n't be transferred in an amount less than the planck 's constant but can be in its multiples ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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does amplitude also determine how much energy a wave carries ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve .
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is the planck constant the minimum energy level for a photon ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves .
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why was there no white spectrum visible ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist .
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in the spectrum table how was the maximum frequency of 10^24 arrived at ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century .
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how do some things give off red light and others yellow ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed .
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if light is just photons what is happening to the photons ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ .
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is energy of photon directly proportional to the brightness of light ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century .
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so , when light travels as a wave what exactly moves in the path of that wave ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons .
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if the frequency in the e=hv equation just a regular letter v ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe .
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in case of light ( the electromagnetic spectrum ) what is the medium through which the disturbance propagates ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ?
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how can a photon have frequency ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health .
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how to measure the frequencies of em radiation in experiments ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation .
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is light referring to all types of electromagnetic radiation ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) .
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as in , it is not only talking about visible light but radio waves and gamma rays would also be considered light ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation .
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do all electromagnetic waves have photons ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation .
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what is the definition of blackbody ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low .
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was there a reason why scientists just assumed that energy in waves is continuous ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ .
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so if the value of e ( the energy of photon absorbed or emitted ) is found , can the number of photons be found ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ .
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i think that photons differ in the degree of frequency , but is a photon just the amount of energy released in each different situation , or is there a specific amount of energy at each level of frequency that equals a discreet photon ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe .
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why hydrogen spectrum has four lines while it has one electron ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low .
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what property separates light waves from all other waves ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves .
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is all light visible to humans ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ .
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does a decrease in wavelength without any change in frequency mean an increase or decrease or no change in the energy of the light ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface .
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electro magnetic waves does n't need any medium but if it pass through any medium will it change anything ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true .
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will heat energy needs a medium ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves .
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if light reflects off of two colored pigments , say cobalt violet and cadmium red colored paints ( two colors on opposite sides of the visible spectrum ) what is physically happening when light is reflected back toward our eye ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century .
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are certain wavelengths of light being absorbed and reflected ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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$ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . )
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what aspects of chemical elements determine there visual color ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) .
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well , when a photon is absorbed by an atom or molecule , how long does it stay there before it is emitted ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) .
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how does a wave oscillates in space ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century .
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how does lava produce light naturally ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) .
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how does earth absorb or block gamma rays from coming ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe .
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is `` light '' another way of saying `` electromagnetic waves '' , meaning that photons are elementary particles of any electromagnetic wave ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation .
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or are photons particles of specific electromagnetic waves such as visible and invisible light , ranging , for example , from uv to ir ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) .
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if frequency and wavelength are inversely proportional , is it correct to say that the period ( t ) is equal to the wavelength ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength .
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in a particular source of light , do all the waves have the same frequency ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) .
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is the photon the elementary particle , or quantum , for only the visible spectrum of light , or for all electromagnetic radiation such as x rays and gamma rays ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true .
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then what is our fundamental currency for trade i.e smallest energy packet ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true .
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and how come energy not continuous and quantised ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains .
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are different photons of atoms of different elements have have same quanta values or different values ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true .
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and that energy is quantized , is this valid for any kind of energy ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true .
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since mechanical energy until eletrical energy , all of these can only be transferred by photons ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example .
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what is the relationship between light + the intensity ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe .
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what is a good example for discontinuous spectrum ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example .
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in the second line of this page where 'heat from a burning fire ' is classified as an electro magnetic wave - and after finding out that all electromagnetic waves travel at the speed of light - does 'heat ' from a fire really travel at the speed of light ?
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introduction to electromagnetic waves electromagnetic radiation is one of the many ways that energy travels through space . the heat from a burning fire , the light from the sun , the x-rays used by your doctor , as well as the energy used to cook food in a microwave are all forms of electromagnetic radiation . while these forms of energy might seem quite different from one another , they are related in that they all exhibit wavelike properties . if you ’ ve ever gone swimming in the ocean , you are already familiar with waves . waves are simply disturbances in a particular physical medium or a field , resulting in a vibration or oscillation . the swell of a wave in the ocean , and the subsequent dip that follows , is simply a vibration or oscillation of the water at the ocean ’ s surface . electromagnetic waves are similar , but they are also distinct in that they actually consist of $ 2 $ waves oscillating perpendicular to one another . one of the waves is an oscillating magnetic field ; the other is an oscillating electric field . this can be visualized as follows : while it ’ s good to have a basic understanding of what electromagnetic radiation is , most chemists are less interested in the physics behind this type of energy , and are far more interested in how these waves interact with matter . more specifically , chemists study how different forms of electromagnetic radiation interact with atoms and molecules . from these interactions , a chemist can get information about a molecule ’ s structure , as well as the types of chemical bonds it contains . before we talk about that , however , it ’ s necessary to talk a little bit more about the physical properties of light waves . basic properties of waves : amplitude , wavelength , and frequency as you might already know , a wave has a trough ( lowest point ) and a crest ( highest point ) . the vertical distance between the tip of a crest and the wave ’ s central axis is known as its amplitude . this is the property associated with the brightness , or intensity , of the wave . the horizontal distance between two consecutive troughs or crests is known as the wavelength of the wave . these lengths can be visualized as follows : keep in mind that some waves ( including electromagnetic waves ) also oscillate in space , and therefore they are oscillating at a given position as time passes . the quantity known as the wave ’ s frequency refers to the number of full wavelengths that pass by a given point in space every second ; the si unit for frequency is hertz $ ( \text { hz } ) $ , which is equivalent to “ per seconds ” $ \big ( $ written as $ \dfrac { 1 } { \text { s } } $ or $ \text { s } ^ { -1 } \big ) $ . as you might imagine , wavelength and frequency are inversely proportional : that is , the shorter the wavelength , the higher the frequency , and vice versa . this relationship is given by the following equation : $ c=\lambda \nu $ where $ \lambda $ ( the greek lambda ) is the wavelength ( in meters , $ \text { m } $ ) and $ \nu $ ( the greek nu ) is the frequency ( in hertz , $ \text { hz } $ ) . their product is the constant $ c $ , the speed of light , which is equal to $ 3.00\times10^8 \text { m/s } $ . this relationship reflects an important fact : all electromagnetic radiation , regardless of wavelength or frequency , travels at the speed of light . to illustrate the relationship between frequency and wavelength , let ’ s consider an example . example : calculating the wavelength of a light wave a particular wave of electromagnetic radiation has a frequency of $ 1.5\times10^ { 14 } \text { hz } $ . what is the wavelength of this wave ? we can start with our equation that relates frequency , wavelength , and the speed of light . $ c=\lambda \nu $ next , we rearrange the equation to solve for wavelength . $ \lambda=\dfrac { c } { \nu } $ lastly , we plug in our given values and solve . $ \lambda=\dfrac { 3.00\times10^8\dfrac { \text { m } } { \cancel { \text { s } } } } { 1.5\times10^ { 14 } \dfrac { 1 } { \cancel { \text { s } } } } =2.00\times10^ { -6 } \text { m } $ concept check : what would you expect to happen to the frequency of a light wave if its wavelength were increased by a factor of $ 10 $ ? period the last quantity we will consider is the period of a wave . a wave ’ s period is the length of time it takes for one wavelength to pass by a given point in space . mathematically , the period ( $ t $ ) is simply the reciprocal of the wave ’ s frequency ( $ f $ ) : $ t=\dfrac { 1 } { f } $ the units of period are seconds ( $ \text { s } $ ) . now that we have an understanding of some basic properties of waves , we ’ ll look at the different types of electromagnetic radiation . the electromagnetic spectrum electromagnetic waves can be classified and arranged according to their various wavelengths/frequencies ; this classification is known as the electromagnetic spectrum . the following table shows us this spectrum , which consists of all the types of electromagnetic radiation that exist in our universe . as we can see , the visible spectrum—that is , light that we can see with our eyes—makes up only a small fraction of the different types of radiation that exist . to the right of the visible spectrum , we find the types of energy that are lower in frequency ( and thus longer in wavelength ) than visible light . these types of energy include infrared ( ir ) rays ( heat waves given off by thermal bodies ) , microwaves , and radio waves . these types of radiation surround us constantly , and are not harmful , because their frequencies are so low . as we will see in the section , “ the photon , ” lower frequency waves are lower in energy , and thus are not dangerous to our health . to the left of the visible spectrum , we have ultraviolet ( uv ) rays , x-rays , and gamma rays . these types of radiation are harmful to living organisms , due to their extremely high frequencies ( and thus , high energies ) . it is for this reason that we wear suntan lotion at the beach ( to block the uv rays from the sun ) and why an x-ray technician will place a lead shield over us , in order to prevent the x-rays from penetrating anything other than the area of our body being imaged . gamma rays , being the highest in frequency and energy , are the most damaging . luckily though , our atmosphere absorbs gamma rays from outer space , thereby protecting us from harm . next , we will talk about the relationship between a wave ’ s frequency and its energy . quantization of energy and the dual nature of light we have already described how light travels through space as a wave . this has been well-known for quite some time ; in fact , the dutch physicist christiaan huygens first described the wave nature of light as far back as the late seventeenth century . for about $ 200 $ years after huygens , physicists assumed that light waves and matter were quite distinct from one another . according to classical physics , matter was composed of particles that had mass , and whose position in space could be known ; light waves , on the other hand , were considered to have zero mass , and their position in space could not be determined . because they were considered to be in different categories , scientists did not have a good understanding of how light and matter interacted . this all changed in $ 1900 $ , however , when the physicist max planck began studying blackbodies – bodies heated until they began to glow . planck found that the electromagnetic radiation emitted by blackbodies could not be explained by classical physics , which postulated that matter could absorb or emit any quantity of electromagnetic radiation . planck observed that matter actually absorbed or emitted energy only in whole-number multiples of the value $ h\nu $ , where $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ , and $ \nu $ is the frequency of the light absorbed or emitted . this was a shocking discovery , because it challenged the idea that energy was continuous , and could be transferred in any amount . the reality , which planck discovered , is that energy is not continuous but quantized—meaning that it can only be transferred in individual “ packets ” ( or particles ) of the size $ h\nu $ . each of these energy packets is known as a quantum ( plural : quanta ) . while this might sound confusing , we are actually already very familiar with quantized systems . the money we use daily , for example , is quantized . for instance , when you go into a store , you will not see anything on sale for a price of one dollar and two and a half cents $ ( \ $ 1.025 ) $ . this is because the smallest possible monetary unit is the penny—it is impossible to transfer money in any smaller amount than this . just as we can not pay the cashier at the store half of a cent , energy can not be transferred in anything less than a single quantum . we can think of quanta as being like “ pennies ” of electromagnetic energy—the smallest possible units by which such energy can be transferred . planck ’ s discovery that electromagnetic radiation is quantized forever changed the idea that light behaves purely as a wave . in actuality , light seemed to have both wavelike and particle-like properties . the photon planck ’ s discoveries paved the way for the discovery of the photon . a photon is the elementary particle , or quantum , of light . as we will soon see , photons can be absorbed or emitted by atoms and molecules . when a photon is absorbed , its energy is transferred to that atom or molecule . because energy is quantized , the photon ’ s entire energy is transferred ( remember that we can not transfer fractions of quanta , which are the smallest possible individual “ energy packets ” ) . the reverse of this process is also true . when an atom or molecule loses energy , it emits a photon that carries an energy exactly equal to the loss in energy of the atom or molecule . this change in energy is directly proportional to the frequency of photon emitted or absorbed . this relationship is given by planck ’ s famous equation : $ e=h\nu $ where $ e $ is the energy of the photon absorbed or emitted ( given in joules , $ \text { j } $ ) , $ \nu $ is frequency of the photon ( given in hertz , $ \text { hz } $ ) , and $ h $ is planck ’ s constant , $ 6.626\times10^ { -34 } \text { j } \cdot\text { s } $ . example : calculating the energy of a photon a photon has a frequency of $ 2.0\times10^ { 24 } \text { hz } $ . what is the energy of this photon ? first , we can apply planck 's equation . $ e=h\nu $ next , we plug in our given value for the frequency , as well as the value for planck 's constant , $ h $ , and solve . $ e= ( 6.626\times10^ { -34 } \text { j } \cdot\cancel { \text { s } } ) \times ( 2.0\times 10^ { 24 } \cancel { \text { s } ^ { -1 } } ) =1.3\times10^ { -9 } \text { j } $ concept check : the wavelength of orange light is about $ 590-635\text { nm } $ , and the wavelength of green light is about $ 520-560\text { nm } $ . which color of light is more energetic , orange or green ? ( hint : keep in mind what you have already learned about the relationship between wavelength and frequency . ) conclusion electromagnetic radiation can be described by its amplitude ( brightness ) , wavelength , frequency , and period . by the equation $ e=h\nu $ , we have seen how the frequency of a light wave is proportional to its energy . at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed . atoms and molecules can also lose energy by emitting photons .
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at the beginning of the twentieth century , the discovery that energy is quantized led to the revelation that light is not only a wave , but can also be described as a collection of particles known as photons . photons carry discrete amounts of energy called quanta . this energy can be transferred to atoms and molecules when photons are absorbed .
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`` photons carry specific amounts of energy called quanta , and this energy can be transferred to atoms and molecules when photons are absorbed '' it says this energy can be transferred , does that mean that sometimes it is n't transferred ?
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