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- sometimes light seems to act as a wave , and sometimes light seems to act as a particle . and , an example of this , would be the photoelectric effect , as described by einstein . so let 's say you had a piece of metal , and we know the metal has electrons . i 'm gon na go ahead and draw one electron in here , and th...
and that energy of the photon is greater than the work function , which means that that 's a high-energy photon . it 's able to knock the electron free , 'cause remember , this number right here , is the minimum amount of energy needed to free the electron and so we 've exceeded that minimum amount of energy , and so w...
is the requirement for light to free electron a minimum amount of energy , or is it a range ?
- sometimes light seems to act as a wave , and sometimes light seems to act as a particle . and , an example of this , would be the photoelectric effect , as described by einstein . so let 's say you had a piece of metal , and we know the metal has electrons . i 'm gon na go ahead and draw one electron in here , and th...
so one photon creates one photoelectron . so one particle hits another particle . and , if you think about this in terms of classical physics , you could think about energy being conserved .
why do we have to think about an electron as particle in photo effect not a wave ?
- sometimes light seems to act as a wave , and sometimes light seems to act as a particle . and , an example of this , would be the photoelectric effect , as described by einstein . so let 's say you had a piece of metal , and we know the metal has electrons . i 'm gon na go ahead and draw one electron in here , and th...
so we can knock it loose , and so let me go ahead and show that . so here , we 're showing the electron being knocked loose and so the electron 's moving in , let 's just say , this direction , with some velocity , v , and if the electron has mass , m , we know that there 's a kinetic energy . the kinetic energy of the...
of electron is knocked out then wo n't it change the configuration of the metal ?
- sometimes light seems to act as a wave , and sometimes light seems to act as a particle . and , an example of this , would be the photoelectric effect , as described by einstein . so let 's say you had a piece of metal , and we know the metal has electrons . i 'm gon na go ahead and draw one electron in here , and th...
so this is kind of like a collision between two particles , if we think about light as being a particle . so i 'm gon na draw in a particle of light which we call a photon , so this is massless , and the photon is going to hit this electron , and if the photon has enough energy , it can free the electron , right ? so w...
is it possible for a photon to knock out multiple electrons ?
- sometimes light seems to act as a wave , and sometimes light seems to act as a particle . and , an example of this , would be the photoelectric effect , as described by einstein . so let 's say you had a piece of metal , and we know the metal has electrons . i 'm gon na go ahead and draw one electron in here , and th...
3.78 times 10 to the negative 19 , and if you did you units up here , you would get joules , and so let 's think about this number for a second , 3.78 times 10 to the negative 19 is the energy of the photon . and that energy of the photon is greater than the work function , which means that that 's a high-energy photon...
energy of a photon is e=hf not hv right ?
- sometimes light seems to act as a wave , and sometimes light seems to act as a particle . and , an example of this , would be the photoelectric effect , as described by einstein . so let 's say you had a piece of metal , and we know the metal has electrons . i 'm gon na go ahead and draw one electron in here , and th...
3.78 times 10 to the negative 19 , and if you did you units up here , you would get joules , and so let 's think about this number for a second , 3.78 times 10 to the negative 19 is the energy of the photon . and that energy of the photon is greater than the work function , which means that that 's a high-energy photon...
does a photon have a finite energy or a finite momentum ?
- sometimes light seems to act as a wave , and sometimes light seems to act as a particle . and , an example of this , would be the photoelectric effect , as described by einstein . so let 's say you had a piece of metal , and we know the metal has electrons . i 'm gon na go ahead and draw one electron in here , and th...
so this is kind of like a collision between two particles , if we think about light as being a particle . so i 'm gon na draw in a particle of light which we call a photon , so this is massless , and the photon is going to hit this electron , and if the photon has enough energy , it can free the electron , right ? so w...
how does light `` hit '' the electron and have an effect on it if on a subatomic level it has no mass ?
- sometimes light seems to act as a wave , and sometimes light seems to act as a particle . and , an example of this , would be the photoelectric effect , as described by einstein . so let 's say you had a piece of metal , and we know the metal has electrons . i 'm gon na go ahead and draw one electron in here , and th...
so one photon creates one photoelectron . so one particle hits another particle . and , if you think about this in terms of classical physics , you could think about energy being conserved .
how can a massless particle knock out an electron ( which has a mass ) ?
- sometimes light seems to act as a wave , and sometimes light seems to act as a particle . and , an example of this , would be the photoelectric effect , as described by einstein . so let 's say you had a piece of metal , and we know the metal has electrons . i 'm gon na go ahead and draw one electron in here , and th...
3.78 times 10 to the negative 19 , and if you did you units up here , you would get joules , and so let 's think about this number for a second , 3.78 times 10 to the negative 19 is the energy of the photon . and that energy of the photon is greater than the work function , which means that that 's a high-energy photon...
what will be the consequence if the work function is equal o the initial energy of the photon ?
- sometimes light seems to act as a wave , and sometimes light seems to act as a particle . and , an example of this , would be the photoelectric effect , as described by einstein . so let 's say you had a piece of metal , and we know the metal has electrons . i 'm gon na go ahead and draw one electron in here , and th...
the problem asked us to solve for the velocity of the photoelectron . so all we have to do is plug in the mass of an electron , which is 9.11 times 10 to the negative 31st kilograms , times v squared . this is equal to 3.5 times 10 to the negative 20 .
in the calculation , does the mass of the photoelectron needs to be converted to grams since 9.11 x 10^31 is in kg ?
- sometimes light seems to act as a wave , and sometimes light seems to act as a particle . and , an example of this , would be the photoelectric effect , as described by einstein . so let 's say you had a piece of metal , and we know the metal has electrons . i 'm gon na go ahead and draw one electron in here , and th...
so the problem says , `` if a photon of wavelength `` 525 nm hits metallic cesium ... '' and so here 's the work function for metallic cesium . `` what is the velocity of the photoelectron produced ? '' so they want to know the velocity of the photoelectron produced , which we know is hiding in the kinetic energy right...
also is the velocity calculated a vector so how do we represent the direction ?
- sometimes light seems to act as a wave , and sometimes light seems to act as a particle . and , an example of this , would be the photoelectric effect , as described by einstein . so let 's say you had a piece of metal , and we know the metal has electrons . i 'm gon na go ahead and draw one electron in here , and th...
some of that energy was needed to free the electron . so the electron was bound , and some of the energy freed the electron . i 'm gon na call that e naught , the energy that freed the electron , and then the rest of that energy must have gone into the kinetic energy of the electron , and so we can write here kinetic e...
this might sound like a stupid question but what happens to the electron once it 's freed out of the metal surface and what happens to the photon ?
- sometimes light seems to act as a wave , and sometimes light seems to act as a particle . and , an example of this , would be the photoelectric effect , as described by einstein . so let 's say you had a piece of metal , and we know the metal has electrons . i 'm gon na go ahead and draw one electron in here , and th...
so this is kind of like a collision between two particles , if we think about light as being a particle . so i 'm gon na draw in a particle of light which we call a photon , so this is massless , and the photon is going to hit this electron , and if the photon has enough energy , it can free the electron , right ? so w...
if f = m x a , and a photon is massless , than how can it knock off an electron ?
- sometimes light seems to act as a wave , and sometimes light seems to act as a particle . and , an example of this , would be the photoelectric effect , as described by einstein . so let 's say you had a piece of metal , and we know the metal has electrons . i 'm gon na go ahead and draw one electron in here , and th...
and , an example of this , would be the photoelectric effect , as described by einstein . so let 's say you had a piece of metal , and we know the metal has electrons . i 'm gon na go ahead and draw one electron in here , and this electron is bound to the metal because it 's attracted to the positive charges in the nuc...
so if enough energy is passed to the atoms in that metal plate , would all the atoms inside become cations and change the properties of that metal ?
- sometimes light seems to act as a wave , and sometimes light seems to act as a particle . and , an example of this , would be the photoelectric effect , as described by einstein . so let 's say you had a piece of metal , and we know the metal has electrons . i 'm gon na go ahead and draw one electron in here , and th...
so we can knock it loose , and so let me go ahead and show that . so here , we 're showing the electron being knocked loose and so the electron 's moving in , let 's just say , this direction , with some velocity , v , and if the electron has mass , m , we know that there 's a kinetic energy . the kinetic energy of the...
how does sal know the mass of the electron ?
- sometimes light seems to act as a wave , and sometimes light seems to act as a particle . and , an example of this , would be the photoelectric effect , as described by einstein . so let 's say you had a piece of metal , and we know the metal has electrons . i 'm gon na go ahead and draw one electron in here , and th...
so this is kind of like a collision between two particles , if we think about light as being a particle . so i 'm gon na draw in a particle of light which we call a photon , so this is massless , and the photon is going to hit this electron , and if the photon has enough energy , it can free the electron , right ? so w...
why does a photon travel 1,000 times faster ( in this example , anyway ) than a photo-electron ?
- sometimes light seems to act as a wave , and sometimes light seems to act as a particle . and , an example of this , would be the photoelectric effect , as described by einstein . so let 's say you had a piece of metal , and we know the metal has electrons . i 'm gon na go ahead and draw one electron in here , and th...
so the problem says , `` if a photon of wavelength `` 525 nm hits metallic cesium ... '' and so here 's the work function for metallic cesium . `` what is the velocity of the photoelectron produced ? '' so they want to know the velocity of the photoelectron produced , which we know is hiding in the kinetic energy right...
so is the velocity of the photoelectron 0m/s or what ?
- sometimes light seems to act as a wave , and sometimes light seems to act as a particle . and , an example of this , would be the photoelectric effect , as described by einstein . so let 's say you had a piece of metal , and we know the metal has electrons . i 'm gon na go ahead and draw one electron in here , and th...
so let me go ahead and highlight that here . so this number is not as high as the work function . the work function was how much energy we needed to free that electron , and since this is lower than the work function that means we do not get a photoelectron . so , you have to have a high enough energy photon in order t...
what happens to the part of the energy 'expended ' to do the work function ?
- sometimes light seems to act as a wave , and sometimes light seems to act as a particle . and , an example of this , would be the photoelectric effect , as described by einstein . so let 's say you had a piece of metal , and we know the metal has electrons . i 'm gon na go ahead and draw one electron in here , and th...
and this e naught , here i 'm calling it e naught , you might see it written differently , a different symbol , but this is the work function . let me go ahead and write work function here , and the work function is different for every kind of metal . so , it 's the minimum amount of energy that 's necessary to free th...
is the work function affected by heat ?
- sometimes light seems to act as a wave , and sometimes light seems to act as a particle . and , an example of this , would be the photoelectric effect , as described by einstein . so let 's say you had a piece of metal , and we know the metal has electrons . i 'm gon na go ahead and draw one electron in here , and th...
it 's able to knock the electron free , 'cause remember , this number right here , is the minimum amount of energy needed to free the electron and so we 've exceeded that minimum amount of energy , and so we will produce a photoelectron . so , this photon is high-energy enough to produce a photoelectron . so let 's go ...
if i put enough photons who have enough energy to remove all the electrons then at the very last , the metal will be without electron ?
- sometimes light seems to act as a wave , and sometimes light seems to act as a particle . and , an example of this , would be the photoelectric effect , as described by einstein . so let 's say you had a piece of metal , and we know the metal has electrons . i 'm gon na go ahead and draw one electron in here , and th...
some of that energy was needed to free the electron . so the electron was bound , and some of the energy freed the electron . i 'm gon na call that e naught , the energy that freed the electron , and then the rest of that energy must have gone into the kinetic energy of the electron , and so we can write here kinetic e...
what is photo-electron rather than being photon partial with electron ?
- sometimes light seems to act as a wave , and sometimes light seems to act as a particle . and , an example of this , would be the photoelectric effect , as described by einstein . so let 's say you had a piece of metal , and we know the metal has electrons . i 'm gon na go ahead and draw one electron in here , and th...
so if we had more and more and more of these photons at this wavelength , we still would n't produce any photoelectrons . and so , this is the idea of the photoelectric effect , which is best explained by thinking about light as a particle .
how is the photoelectric effect evidence that light has particle nature ?
- sometimes light seems to act as a wave , and sometimes light seems to act as a particle . and , an example of this , would be the photoelectric effect , as described by einstein . so let 's say you had a piece of metal , and we know the metal has electrons . i 'm gon na go ahead and draw one electron in here , and th...
so if we had more and more and more of these photons at this wavelength , we still would n't produce any photoelectrons . and so , this is the idea of the photoelectric effect , which is best explained by thinking about light as a particle .
why ca n't wave nature of light explain photoelectric effect ?
- sometimes light seems to act as a wave , and sometimes light seems to act as a particle . and , an example of this , would be the photoelectric effect , as described by einstein . so let 's say you had a piece of metal , and we know the metal has electrons . i 'm gon na go ahead and draw one electron in here , and th...
and , if you think about this in terms of classical physics , you could think about energy being conserved . so the energy of the photon , the energy that went in , so let me go ahead and write this here , so the energy of the photon , the energy that went in , what happened to that energy ? some of that energy was nee...
how do you know if it is just one photon with an energy of say , x or multiple photons with a cumulative energy of x which dislodges the electron ?
- sometimes light seems to act as a wave , and sometimes light seems to act as a particle . and , an example of this , would be the photoelectric effect , as described by einstein . so let 's say you had a piece of metal , and we know the metal has electrons . i 'm gon na go ahead and draw one electron in here , and th...
so , you have to have a high enough energy photon in order to produce a photoelectron . it would n't even matter if we increased the intensity . so if we had more and more and more of these photons at this wavelength , we still would n't produce any photoelectrons . and so , this is the idea of the photoelectric effect...
also we are talking about classical mechanics is n't the photons motion supposed to be studied by quantum mechanics ?
- sometimes light seems to act as a wave , and sometimes light seems to act as a particle . and , an example of this , would be the photoelectric effect , as described by einstein . so let 's say you had a piece of metal , and we know the metal has electrons . i 'm gon na go ahead and draw one electron in here , and th...
so let 's think about this same problem , but let 's change the wavelength . so , what if your wavelength changed to 625 nanometers . so what would happen now ?
if the wavelength of the photon was 625 nm then what would 've happened ?
- sometimes light seems to act as a wave , and sometimes light seems to act as a particle . and , an example of this , would be the photoelectric effect , as described by einstein . so let 's say you had a piece of metal , and we know the metal has electrons . i 'm gon na go ahead and draw one electron in here , and th...
so , what if your wavelength changed to 625 nanometers . so what would happen now ? well , to save time , i wo n't do the calculation , but all we would have to do is plug in 625 up here .
would the photons just pass through cesium without affecting it or would cesium be transparent for the 625 nm wavelength light ( probably orange ) or would something else happen entirely ?
- sometimes light seems to act as a wave , and sometimes light seems to act as a particle . and , an example of this , would be the photoelectric effect , as described by einstein . so let 's say you had a piece of metal , and we know the metal has electrons . i 'm gon na go ahead and draw one electron in here , and th...
3.78 times 10 to the negative 19 , and if you did you units up here , you would get joules , and so let 's think about this number for a second , 3.78 times 10 to the negative 19 is the energy of the photon . and that energy of the photon is greater than the work function , which means that that 's a high-energy photon...
if so then what exactly does happen when the energy of the photon is less than the work function of the metal it hits ?
- sometimes light seems to act as a wave , and sometimes light seems to act as a particle . and , an example of this , would be the photoelectric effect , as described by einstein . so let 's say you had a piece of metal , and we know the metal has electrons . i 'm gon na go ahead and draw one electron in here , and th...
3.78 times 10 to the negative 19 , and if you did you units up here , you would get joules , and so let 's think about this number for a second , 3.78 times 10 to the negative 19 is the energy of the photon . and that energy of the photon is greater than the work function , which means that that 's a high-energy photon...
if the photon does not have enough energy to knock the electron free , that is if the energy of the photon is less than the work function , what happens then ?
- sometimes light seems to act as a wave , and sometimes light seems to act as a particle . and , an example of this , would be the photoelectric effect , as described by einstein . so let 's say you had a piece of metal , and we know the metal has electrons . i 'm gon na go ahead and draw one electron in here , and th...
so we can knock it loose , and so let me go ahead and show that . so here , we 're showing the electron being knocked loose and so the electron 's moving in , let 's just say , this direction , with some velocity , v , and if the electron has mass , m , we know that there 's a kinetic energy . the kinetic energy of the...
does the electron have a negative velocity in that case ?
- sometimes light seems to act as a wave , and sometimes light seems to act as a particle . and , an example of this , would be the photoelectric effect , as described by einstein . so let 's say you had a piece of metal , and we know the metal has electrons . i 'm gon na go ahead and draw one electron in here , and th...
i 'm gon na go ahead and draw one electron in here , and this electron is bound to the metal because it 's attracted to the positive charges in the nucleus . if you shine a light on the metal , so the right kind of light with the right kind of frequency , you can actually knock some of those electrons loose , which cau...
could you fine tune the frequency of the light so the electrons velocity is visible to the human eye ?
- sometimes light seems to act as a wave , and sometimes light seems to act as a particle . and , an example of this , would be the photoelectric effect , as described by einstein . so let 's say you had a piece of metal , and we know the metal has electrons . i 'm gon na go ahead and draw one electron in here , and th...
so this is kind of like a collision between two particles , if we think about light as being a particle . so i 'm gon na draw in a particle of light which we call a photon , so this is massless , and the photon is going to hit this electron , and if the photon has enough energy , it can free the electron , right ? so w...
how would the photon knock the electron without any mass ?
- sometimes light seems to act as a wave , and sometimes light seems to act as a particle . and , an example of this , would be the photoelectric effect , as described by einstein . so let 's say you had a piece of metal , and we know the metal has electrons . i 'm gon na go ahead and draw one electron in here , and th...
so this is kind of like a collision between two particles , if we think about light as being a particle . so i 'm gon na draw in a particle of light which we call a photon , so this is massless , and the photon is going to hit this electron , and if the photon has enough energy , it can free the electron , right ? so w...
does a photon with a smaller wavelength cause an electron on the metal surface to be ejected with a greater velocity ?
- sometimes light seems to act as a wave , and sometimes light seems to act as a particle . and , an example of this , would be the photoelectric effect , as described by einstein . so let 's say you had a piece of metal , and we know the metal has electrons . i 'm gon na go ahead and draw one electron in here , and th...
if you shine a light on the metal , so the right kind of light with the right kind of frequency , you can actually knock some of those electrons loose , which causes a current of electrons to flow . so this is kind of like a collision between two particles , if we think about light as being a particle . so i 'm gon na ...
do photons ever emerge or combine like waves do ?
- sometimes light seems to act as a wave , and sometimes light seems to act as a particle . and , an example of this , would be the photoelectric effect , as described by einstein . so let 's say you had a piece of metal , and we know the metal has electrons . i 'm gon na go ahead and draw one electron in here , and th...
3.78 times 10 to the negative 19 , and if you did you units up here , you would get joules , and so let 's think about this number for a second , 3.78 times 10 to the negative 19 is the energy of the photon . and that energy of the photon is greater than the work function , which means that that 's a high-energy photon...
but sal , what exactly happens to the photon ( and its energy ) when its energy is less than the work function ?
- sometimes light seems to act as a wave , and sometimes light seems to act as a particle . and , an example of this , would be the photoelectric effect , as described by einstein . so let 's say you had a piece of metal , and we know the metal has electrons . i 'm gon na go ahead and draw one electron in here , and th...
so this is kind of like a collision between two particles , if we think about light as being a particle . so i 'm gon na draw in a particle of light which we call a photon , so this is massless , and the photon is going to hit this electron , and if the photon has enough energy , it can free the electron , right ? so w...
who decided that a photon was massless ?
- sometimes light seems to act as a wave , and sometimes light seems to act as a particle . and , an example of this , would be the photoelectric effect , as described by einstein . so let 's say you had a piece of metal , and we know the metal has electrons . i 'm gon na go ahead and draw one electron in here , and th...
i 'm gon na go ahead and draw one electron in here , and this electron is bound to the metal because it 's attracted to the positive charges in the nucleus . if you shine a light on the metal , so the right kind of light with the right kind of frequency , you can actually knock some of those electrons loose , which cau...
does this mean we can generate electric current using electromagnetic radiation ?
- sometimes light seems to act as a wave , and sometimes light seems to act as a particle . and , an example of this , would be the photoelectric effect , as described by einstein . so let 's say you had a piece of metal , and we know the metal has electrons . i 'm gon na go ahead and draw one electron in here , and th...
the frequency is equal to speed of light over lambda , so we can plug that into here , and so now we have the energy of the photon is equal to hc over lambda , and we can plug in those numbers . h is planck 's constant , which is 6.626 times 10 to the negative 34 . so , times 10 to the negative 34 here .
what is planck 's constant ?
- sometimes light seems to act as a wave , and sometimes light seems to act as a particle . and , an example of this , would be the photoelectric effect , as described by einstein . so let 's say you had a piece of metal , and we know the metal has electrons . i 'm gon na go ahead and draw one electron in here , and th...
c is the speed of light , which is 2.998 times 10 to the 8th meters over seconds , and all over lambda . lambda is the wavelength . that 's 525 nanometers .
can wavelength be expressed in any other form like m , cm , km ?
- sometimes light seems to act as a wave , and sometimes light seems to act as a particle . and , an example of this , would be the photoelectric effect , as described by einstein . so let 's say you had a piece of metal , and we know the metal has electrons . i 'm gon na go ahead and draw one electron in here , and th...
c is the speed of light , which is 2.998 times 10 to the 8th meters over seconds , and all over lambda . lambda is the wavelength . that 's 525 nanometers .
why is wavelength expressed in nm ?
- sometimes light seems to act as a wave , and sometimes light seems to act as a particle . and , an example of this , would be the photoelectric effect , as described by einstein . so let 's say you had a piece of metal , and we know the metal has electrons . i 'm gon na go ahead and draw one electron in here , and th...
- sometimes light seems to act as a wave , and sometimes light seems to act as a particle . and , an example of this , would be the photoelectric effect , as described by einstein . so let 's say you had a piece of metal , and we know the metal has electrons .
why ca n't we explain photo effect in terms of wave nature of light ?
- sometimes light seems to act as a wave , and sometimes light seems to act as a particle . and , an example of this , would be the photoelectric effect , as described by einstein . so let 's say you had a piece of metal , and we know the metal has electrons . i 'm gon na go ahead and draw one electron in here , and th...
i 'm gon na go ahead and draw one electron in here , and this electron is bound to the metal because it 's attracted to the positive charges in the nucleus . if you shine a light on the metal , so the right kind of light with the right kind of frequency , you can actually knock some of those electrons loose , which cau...
so if you shine white light on a metal , it will knock electrons off for sure , because white light contains all wavelengths of visible light ?
- sometimes light seems to act as a wave , and sometimes light seems to act as a particle . and , an example of this , would be the photoelectric effect , as described by einstein . so let 's say you had a piece of metal , and we know the metal has electrons . i 'm gon na go ahead and draw one electron in here , and th...
so one particle hits another particle . and , if you think about this in terms of classical physics , you could think about energy being conserved . so the energy of the photon , the energy that went in , so let me go ahead and write this here , so the energy of the photon , the energy that went in , what happened to t...
so my question is after this stage of we still supply ( sufficient ) energy photons , then from where will the electrons be emitted- from the next orbit or from the next layer of atoms ?
- sometimes light seems to act as a wave , and sometimes light seems to act as a particle . and , an example of this , would be the photoelectric effect , as described by einstein . so let 's say you had a piece of metal , and we know the metal has electrons . i 'm gon na go ahead and draw one electron in here , and th...
so this is kind of like a collision between two particles , if we think about light as being a particle . so i 'm gon na draw in a particle of light which we call a photon , so this is massless , and the photon is going to hit this electron , and if the photon has enough energy , it can free the electron , right ? so w...
when a photon collides with an electron to crate a photo electron , is the energy in the photon being transferred to the electron in quanta so that the atom is in the excited state for a moment and the resulting light is spectra ?
- sometimes light seems to act as a wave , and sometimes light seems to act as a particle . and , an example of this , would be the photoelectric effect , as described by einstein . so let 's say you had a piece of metal , and we know the metal has electrons . i 'm gon na go ahead and draw one electron in here , and th...
some of that energy was needed to free the electron . so the electron was bound , and some of the energy freed the electron . i 'm gon na call that e naught , the energy that freed the electron , and then the rest of that energy must have gone into the kinetic energy of the electron , and so we can write here kinetic e...
or is the electron totally freed from its atom making a positive ion before it loses enough to kinetic energy to be brought into another orbital ?
- sometimes light seems to act as a wave , and sometimes light seems to act as a particle . and , an example of this , would be the photoelectric effect , as described by einstein . so let 's say you had a piece of metal , and we know the metal has electrons . i 'm gon na go ahead and draw one electron in here , and th...
i 'm gon na call that e naught , the energy that freed the electron , and then the rest of that energy must have gone into the kinetic energy of the electron , and so we can write here kinetic energy of the photoelectron that was produced . so , kinetic energy of the photoelectron . so let 's say you wanted to solve fo...
there is a usage of the term photoelectron , what does it actually mean ?
- sometimes light seems to act as a wave , and sometimes light seems to act as a particle . and , an example of this , would be the photoelectric effect , as described by einstein . so let 's say you had a piece of metal , and we know the metal has electrons . i 'm gon na go ahead and draw one electron in here , and th...
so let 's think about this same problem , but let 's change the wavelength . so , what if your wavelength changed to 625 nanometers . so what would happen now ?
if i were to say i had to convert all my meters of wavelength to nanometers , how would i convert meters to nanometers ?
- sometimes light seems to act as a wave , and sometimes light seems to act as a particle . and , an example of this , would be the photoelectric effect , as described by einstein . so let 's say you had a piece of metal , and we know the metal has electrons . i 'm gon na go ahead and draw one electron in here , and th...
so , what if your wavelength changed to 625 nanometers . so what would happen now ? well , to save time , i wo n't do the calculation , but all we would have to do is plug in 625 up here .
what kind of equation would be used ?
- sometimes light seems to act as a wave , and sometimes light seems to act as a particle . and , an example of this , would be the photoelectric effect , as described by einstein . so let 's say you had a piece of metal , and we know the metal has electrons . i 'm gon na go ahead and draw one electron in here , and th...
so , it 's the minimum amount of energy that 's necessary to free the electron , and so obviously that 's going to be different depending on what metal you 're talking about . all right , let 's do a problem . now that we understand the general idea of the photoelectric effect , let 's look at what this problem asks us...
so the battery is connected to keep the plates at different potential , and still the circuit is incomplete unless photons are bombarded , right ?
- sometimes light seems to act as a wave , and sometimes light seems to act as a particle . and , an example of this , would be the photoelectric effect , as described by einstein . so let 's say you had a piece of metal , and we know the metal has electrons . i 'm gon na go ahead and draw one electron in here , and th...
so , what if your wavelength changed to 625 nanometers . so what would happen now ? well , to save time , i wo n't do the calculation , but all we would have to do is plug in 625 up here .
also , does it ever happen that the cathode gets much positive charge and anode , negative charge , so that the current decreases in the given direction , or even stops ?
- sometimes light seems to act as a wave , and sometimes light seems to act as a particle . and , an example of this , would be the photoelectric effect , as described by einstein . so let 's say you had a piece of metal , and we know the metal has electrons . i 'm gon na go ahead and draw one electron in here , and th...
i 'm gon na go ahead and draw one electron in here , and this electron is bound to the metal because it 's attracted to the positive charges in the nucleus . if you shine a light on the metal , so the right kind of light with the right kind of frequency , you can actually knock some of those electrons loose , which cau...
if you have a really bright , really massive purple light compared to a small , dim purple light would the larger , brighter one cause more electrons to be liberated ?
- sometimes light seems to act as a wave , and sometimes light seems to act as a particle . and , an example of this , would be the photoelectric effect , as described by einstein . so let 's say you had a piece of metal , and we know the metal has electrons . i 'm gon na go ahead and draw one electron in here , and th...
3.78 times 10 to the negative 19 , and if you did you units up here , you would get joules , and so let 's think about this number for a second , 3.78 times 10 to the negative 19 is the energy of the photon . and that energy of the photon is greater than the work function , which means that that 's a high-energy photon...
if the energy of the photon is lesser than the work function , why ca n't the electron absorb another photon to meet it 's energy requirements ?
- sometimes light seems to act as a wave , and sometimes light seems to act as a particle . and , an example of this , would be the photoelectric effect , as described by einstein . so let 's say you had a piece of metal , and we know the metal has electrons . i 'm gon na go ahead and draw one electron in here , and th...
so let me go ahead and highlight that here . so this number is not as high as the work function . the work function was how much energy we needed to free that electron , and since this is lower than the work function that means we do not get a photoelectron . so , you have to have a high enough energy photon in order t...
for what energy level is work function valid ?
- sometimes light seems to act as a wave , and sometimes light seems to act as a particle . and , an example of this , would be the photoelectric effect , as described by einstein . so let 's say you had a piece of metal , and we know the metal has electrons . i 'm gon na go ahead and draw one electron in here , and th...
so the energy of the photon , the energy that went in , so let me go ahead and write this here , so the energy of the photon , the energy that went in , what happened to that energy ? some of that energy was needed to free the electron . so the electron was bound , and some of the energy freed the electron . i 'm gon n...
if the photon has enough energy to knock out 2 electron , so will it knock electron with higher speed or will it knock out two electron ?
- we 've been looking at the titration curve for the titration of a strong acid , hcl , with a strong base , naoh . in the previous video , we 've already found the ph at two points on our titration curve , so we found the ph before we 'd added any of our base , we found the ph at this point , and we also found the ph ...
so all of our base is going to react , and it 's going to completely neutralize our acids . so when that happens , the ph should be just the ph of water . the ph of our solution should be the ph of water , which we know is equal to seven , so 7.00 i could have written this another way .
what is the ph level of soil from the sahara desert ?
- we 've been looking at the titration curve for the titration of a strong acid , hcl , with a strong base , naoh . in the previous video , we 've already found the ph at two points on our titration curve , so we found the ph before we 'd added any of our base , we found the ph at this point , and we also found the ph ...
okay , remember : the hydroxide ions reacted with the hydronium ions . we talked about the fact that h3o+ plus oh- gives us 2h2o . this time , we 're starting with .0101 moles of hydroxide ions .
why does dave insert the negative sign on the top of the o instead of at the end of oh ?
- we 've been looking at the titration curve for the titration of a strong acid , hcl , with a strong base , naoh . in the previous video , we 've already found the ph at two points on our titration curve , so we found the ph before we 'd added any of our base , we found the ph at this point , and we also found the ph ...
how many liters are we adding ? well , 20.20 mls , is the same thing as .02020 liters . so , we just need to solve for moles ; and you can probably do this in your head .
is there any way to calculate mathemetically that the ph becomes 7 when 20 ml of naoh neutralizes 20 ml of hcl ?
- we 've been looking at the titration curve for the titration of a strong acid , hcl , with a strong base , naoh . in the previous video , we 've already found the ph at two points on our titration curve , so we found the ph before we 'd added any of our base , we found the ph at this point , and we also found the ph ...
i 'm just going to use the calculator here to show you the answer . so : .5 x .02020 , gives us .0101 so that 's how many moles of hydroxide ions we have : .0101 moles of hydroxide ions . okay , remember : the hydroxide ions reacted with the hydronium ions . we talked about the fact that h3o+ plus oh- gives us 2h2o .
how do we know that all the hydrogen ions and hydroxide ions will react to form water ?
- we 've been looking at the titration curve for the titration of a strong acid , hcl , with a strong base , naoh . in the previous video , we 've already found the ph at two points on our titration curve , so we found the ph before we 'd added any of our base , we found the ph at this point , and we also found the ph ...
i could have written : hcl + naoh , right ? this would give us , this would give us h2o , 'cause h+ and oh- give us h2o , and then we would have nacl left , right ? we would have a solution of sodium chloride .
would n't the concentration of h+ be zero and therefore the ph = - log [ 0 ] ?
- we 've been looking at the titration curve for the titration of a strong acid , hcl , with a strong base , naoh . in the previous video , we 've already found the ph at two points on our titration curve , so we found the ph before we 'd added any of our base , we found the ph at this point , and we also found the ph ...
this would give us , this would give us h2o , 'cause h+ and oh- give us h2o , and then we would have nacl left , right ? we would have a solution of sodium chloride . so , an aqueous solution of sodium chloride . and , if our acid and our base completely neutralize each other , we 're just left with an aqueous solution...
how do we know that the sodium ions and the chloride anions do n't interact with water to affect ph ?
- we 've been looking at the titration curve for the titration of a strong acid , hcl , with a strong base , naoh . in the previous video , we 've already found the ph at two points on our titration curve , so we found the ph before we 'd added any of our base , we found the ph at this point , and we also found the ph ...
so we have : .01 moles of base , and that 's the same number of moles of acid that we have . so .01 moles of acids . so , this time , we have enough base to completely neutralize our acids .
what are some of the acids and bases that are mostly used in titration ?
- we 've been looking at the titration curve for the titration of a strong acid , hcl , with a strong base , naoh . in the previous video , we 've already found the ph at two points on our titration curve , so we found the ph before we 'd added any of our base , we found the ph at this point , and we also found the ph ...
so 20 mls of base added , the ph should be seven , so we can find this point on our titration curve . this is the equivalence point . so let me go ahead and draw a line down here .
is equivalence pt the same as end point ?
- we 've been looking at the titration curve for the titration of a strong acid , hcl , with a strong base , naoh . in the previous video , we 've already found the ph at two points on our titration curve , so we found the ph before we 'd added any of our base , we found the ph at this point , and we also found the ph ...
- we 've been looking at the titration curve for the titration of a strong acid , hcl , with a strong base , naoh . in the previous video , we 've already found the ph at two points on our titration curve , so we found the ph before we 'd added any of our base , we found the ph at this point , and we also found the ph ...
is the equivalence point for a strong acid and strong base always a ph of 7 ?
- we 've been looking at the titration curve for the titration of a strong acid , hcl , with a strong base , naoh . in the previous video , we 've already found the ph at two points on our titration curve , so we found the ph before we 'd added any of our base , we found the ph at this point , and we also found the ph ...
so we 're gon na get the same , we 're gon na lose the same amount of base , so we 're gon na lose .0100 moles of base , and so we 're left with a very small amount of base . we 're left with .0001 moles of base left over . so all of the acid has been completely neutralized and we have a small amount of base left over ...
how do you know that the h30 does n't remain , but that there is some base left over ?
- we 've been looking at the titration curve for the titration of a strong acid , hcl , with a strong base , naoh . in the previous video , we 've already found the ph at two points on our titration curve , so we found the ph before we 'd added any of our base , we found the ph at this point , and we also found the ph ...
in the previous video , we 've already found the ph at two points on our titration curve , so we found the ph before we 'd added any of our base , we found the ph at this point , and we also found the ph after we added 10 mls of our base , we found the ph at this point . this is part a of our question , this is part b ...
are the significant figures correct in the calculation of part d ?
let 's say there are two communities , an orange community and a purple community , and they 're separate from each other . and your job is to go into these communities , and find out what the most common influenza type is that 's circulating among the people . so you do this , and the first thing you discover is somet...
and those little mutations you can see with the yellow x 's . so what would we call this process ? we call it genetic drift .
would the swine flu ( h1n1 ) that happened at around 2008-09 be considered a pandemic ?
let 's say there are two communities , an orange community and a purple community , and they 're separate from each other . and your job is to go into these communities , and find out what the most common influenza type is that 's circulating among the people . so you do this , and the first thing you discover is somet...
so let me actually write that over here , type a . and if you go over to the purple community , you actually find quite the opposite . you find that over here , people are also getting the flu , but it 's always because of type b .
where can we go to find out which strain is in the population ?
let 's say there are two communities , an orange community and a purple community , and they 're separate from each other . and your job is to go into these communities , and find out what the most common influenza type is that 's circulating among the people . so you do this , and the first thing you discover is somet...
so what would we call this process ? we call it genetic drift . this is genetic drift . this is kind of the normal process that happens with many , many types of viruses and bacteria .
if a genetic shift is responsible for pandemics , then why was the swine flu ( h1n1 ) in 2009 a pandemic ?
let 's say there are two communities , an orange community and a purple community , and they 're separate from each other . and your job is to go into these communities , and find out what the most common influenza type is that 's circulating among the people . so you do this , and the first thing you discover is somet...
let 's plot that a little bit higher . so now the virus , the type b virus , is looking slightly different from how it was when you first started the job . and you keep going with this process , and you know , there 's a mutation here , another one over here .
if it were impossible for two different strains of a virus to attack the same cell would it then be impossible for a virus to shift/drift ?
let 's say there are two communities , an orange community and a purple community , and they 're separate from each other . and your job is to go into these communities , and find out what the most common influenza type is that 's circulating among the people . so you do this , and the first thing you discover is somet...
and if you go over to the purple community , you actually find quite the opposite . you find that over here , people are also getting the flu , but it 's always because of type b . so these people over here are having influenza type b .
or is it possible for a strain of type a flu to genetically change/mutate without mixing with another ?
the illustration below shows the graph of y as a function of x . so that 's this graph right over here . and then they start to ask us some questions . complete the sentences based on the graph of the function . so this axis is our y-axis , the vertical axis . horizontal axis is x-axis . initially , as x increases -- s...
so as x increases initially , y decreases . the slope of the graph is equal to blank for all x between x equals 0 and x equals 3 . so x equals 0 and x equals 3 , what 's the slope ? well , every time we move 1 in the x direction , we move down in the y direction .
what 's the slope of sal 's function when x is 3 ?
the illustration below shows the graph of y as a function of x . so that 's this graph right over here . and then they start to ask us some questions . complete the sentences based on the graph of the function . so this axis is our y-axis , the vertical axis . horizontal axis is x-axis . initially , as x increases -- s...
and then they start to ask us some questions . complete the sentences based on the graph of the function . so this axis is our y-axis , the vertical axis .
what is a `` constant function '' ?
the illustration below shows the graph of y as a function of x . so that 's this graph right over here . and then they start to ask us some questions . complete the sentences based on the graph of the function . so this axis is our y-axis , the vertical axis . horizontal axis is x-axis . initially , as x increases -- s...
and then they start to ask us some questions . complete the sentences based on the graph of the function . so this axis is our y-axis , the vertical axis .
can different style of line graphs affect how you interpret the function ?
the illustration below shows the graph of y as a function of x . so that 's this graph right over here . and then they start to ask us some questions . complete the sentences based on the graph of the function . so this axis is our y-axis , the vertical axis . horizontal axis is x-axis . initially , as x increases -- s...
the illustration below shows the graph of y as a function of x . so that 's this graph right over here .
what is the difference between linear functions and nonlinear functions ?
the illustration below shows the graph of y as a function of x . so that 's this graph right over here . and then they start to ask us some questions . complete the sentences based on the graph of the function . so this axis is our y-axis , the vertical axis . horizontal axis is x-axis . initially , as x increases -- s...
so let 's make sure that we did n't make any careless mistakes here . let 's check our answer . we got it right .
parcc test practice http : //parcc.pearson.com/resources/practice_tests/grade_8/math/pc194840-001_g8mathoptb_pt.pdf what is the answer of graph problem in page 7 ?
so this might surprise you , but one of the most amazing feats you 'll ever accomplish as a human being already happened , and that is language development . i mean , think about it . when you 're a baby , all these sounds are coming at you , and somehow , you 're able to figure out which sounds are words , where there...
it 's just an idea that this ability exists . and this works because he thought that all languages shared a universal grammar , or the same basic elements , so all languages would have nouns , verbs , things like that . so the language acquisition device enables the child to pick up on and understand those types of wor...
has anyone ever wondered why so many languages have similar words for moms ?
so this might surprise you , but one of the most amazing feats you 'll ever accomplish as a human being already happened , and that is language development . i mean , think about it . when you 're a baby , all these sounds are coming at you , and somehow , you 're able to figure out which sounds are words , where there...
once you start using it , then it specializes to your language , and it becomes unable to detect other sounds and grammar from other languages . the second theory i want to tell you about is the learning theory . learning theorists think that children are n't born with anything .
also , is `` learning theory '' interchangeable with `` behaviorist theory '' ?
so this might surprise you , but one of the most amazing feats you 'll ever accomplish as a human being already happened , and that is language development . i mean , think about it . when you 're a baby , all these sounds are coming at you , and somehow , you 're able to figure out which sounds are words , where there...
it 's just an idea that this ability exists . and this works because he thought that all languages shared a universal grammar , or the same basic elements , so all languages would have nouns , verbs , things like that . so the language acquisition device enables the child to pick up on and understand those types of wor...
so if a child ( who has the ability to recognize and pick-up languages ) lived for short periods , perhaps a year in 3 different countries , would he/she be able to speak all three languages ?
so this might surprise you , but one of the most amazing feats you 'll ever accomplish as a human being already happened , and that is language development . i mean , think about it . when you 're a baby , all these sounds are coming at you , and somehow , you 're able to figure out which sounds are words , where there...
learning theorists think that children are n't born with anything . they only acquire language through reinforcement . so a learning theorist would say that a child learns to say `` mama '' because every time it makes it sound that approaches that -- so `` ma-something '' -- then mom starts smiling , hugging the child ...
does anyone know if it is easier to acquire language for adults who already know a certain number of languages ?
so this might surprise you , but one of the most amazing feats you 'll ever accomplish as a human being already happened , and that is language development . i mean , think about it . when you 're a baby , all these sounds are coming at you , and somehow , you 're able to figure out which sounds are words , where there...
once you start using it , then it specializes to your language , and it becomes unable to detect other sounds and grammar from other languages . the second theory i want to tell you about is the learning theory . learning theorists think that children are n't born with anything . they only acquire language through rein...
is there a climax number , after which learning becomes easier ( analogous to the activation energy of a reaction or hiking to the top of the mountain ) ?
so this might surprise you , but one of the most amazing feats you 'll ever accomplish as a human being already happened , and that is language development . i mean , think about it . when you 're a baby , all these sounds are coming at you , and somehow , you 're able to figure out which sounds are words , where there...
and the main guy associated with this theory is noam chomsky . and he thought the humans had something called a language acquisition device , or lad , in their brains that allowed them to learn language . and this is n't really supposed to be in a specific part of the brain .
my question will be is there any ways to produce the lad to help people learn languages ?
so this might surprise you , but one of the most amazing feats you 'll ever accomplish as a human being already happened , and that is language development . i mean , think about it . when you 're a baby , all these sounds are coming at you , and somehow , you 're able to figure out which sounds are words , where there...
so this makes sense . but a strict learning theory does n't explain how children are able to produce words they 've never heard before or produce unique sentences . so we have another theory called the interactionist approach .
how can we disprove the idea within the learning theory that children will sometimes use words and/or phrases they 've never heard before ?
so this might surprise you , but one of the most amazing feats you 'll ever accomplish as a human being already happened , and that is language development . i mean , think about it . when you 're a baby , all these sounds are coming at you , and somehow , you 're able to figure out which sounds are words , where there...
so this makes sense . but a strict learning theory does n't explain how children are able to produce words they 've never heard before or produce unique sentences . so we have another theory called the interactionist approach .
more specifically , how can we be sure that these new words were not picked up passively from sources that the parents/observers/researchers were n't aware of ?
so this might surprise you , but one of the most amazing feats you 'll ever accomplish as a human being already happened , and that is language development . i mean , think about it . when you 're a baby , all these sounds are coming at you , and somehow , you 're able to figure out which sounds are words , where there...
and this works because he thought that all languages shared a universal grammar , or the same basic elements , so all languages would have nouns , verbs , things like that . so the language acquisition device enables the child to pick up on and understand those types of words and their organization within a sentence fo...
which theory of language development you find the best in developing of the language of a child ?
how do we count the flowers ? so , this first choice , they go one , two , three , and then they do n't count this one and then they skip it and they go four , five , six , and then they skip this one again , and then they say seven , eight . that 's not how you count flowers ! you 'd say this is four , this is five ,...
let 's keep going . type the missing numbers . it says count the ladybugs .
to count numbers in order , you basically just need to memorize the numbers and what order they come in right ?
how do we count the flowers ? so , this first choice , they go one , two , three , and then they do n't count this one and then they skip it and they go four , five , six , and then they skip this one again , and then they say seven , eight . that 's not how you count flowers ! you 'd say this is four , this is five ,...
it 's a lot of fun . count the flowers . type the missing numbers in the boxes .
do we have to count from zero ?
how do we count the flowers ? so , this first choice , they go one , two , three , and then they do n't count this one and then they skip it and they go four , five , six , and then they skip this one again , and then they say seven , eight . that 's not how you count flowers ! you 'd say this is four , this is five ,...
it 's a lot of fun . count the flowers . type the missing numbers in the boxes .
why do we count things ?
how do we count the flowers ? so , this first choice , they go one , two , three , and then they do n't count this one and then they skip it and they go four , five , six , and then they skip this one again , and then they say seven , eight . that 's not how you count flowers ! you 'd say this is four , this is five ,...
it 's a lot of fun . count the flowers . type the missing numbers in the boxes .
why is it important to count in order ?
how do we count the flowers ? so , this first choice , they go one , two , three , and then they do n't count this one and then they skip it and they go four , five , six , and then they skip this one again , and then they say seven , eight . that 's not how you count flowers ! you 'd say this is four , this is five ,...
that one looks good so i 'll click right over here and check my answer . how do we count the mice ? let 's see , one , two , this is n't the third mouse !
why did you use mice to count ?
how do we count the flowers ? so , this first choice , they go one , two , three , and then they do n't count this one and then they skip it and they go four , five , six , and then they skip this one again , and then they say seven , eight . that 's not how you count flowers ! you 'd say this is four , this is five ,...
let 's keep going . type the missing numbers . it says count the ladybugs .
are there numbers after 100 ?
how do we count the flowers ? so , this first choice , they go one , two , three , and then they do n't count this one and then they skip it and they go four , five , six , and then they skip this one again , and then they say seven , eight . that 's not how you count flowers ! you 'd say this is four , this is five ,...
let 's keep going . type the missing numbers . it says count the ladybugs .
why do we have numbers ?
how do we count the flowers ? so , this first choice , they go one , two , three , and then they do n't count this one and then they skip it and they go four , five , six , and then they skip this one again , and then they say seven , eight . that 's not how you count flowers ! you 'd say this is four , this is five ,...
so , we saw one like this a few questions ago . one , two , three , four , five , six , seven , eight , nine , 10 . that one looks good .
what is -5 divided by 2 , 2.5 or -10 or 10 or -2.5 ?
how do we count the flowers ? so , this first choice , they go one , two , three , and then they do n't count this one and then they skip it and they go four , five , six , and then they skip this one again , and then they say seven , eight . that 's not how you count flowers ! you 'd say this is four , this is five ,...
it 's a lot of fun . count the flowers . type the missing numbers in the boxes .
how do we know that we 're supposed to count flowers like americans count ?
how do we count the flowers ? so , this first choice , they go one , two , three , and then they do n't count this one and then they skip it and they go four , five , six , and then they skip this one again , and then they say seven , eight . that 's not how you count flowers ! you 'd say this is four , this is five ,...
it 's a lot of fun . count the flowers . type the missing numbers in the boxes .
why do we count in base 10 ?
how do we count the flowers ? so , this first choice , they go one , two , three , and then they do n't count this one and then they skip it and they go four , five , six , and then they skip this one again , and then they say seven , eight . that 's not how you count flowers ! you 'd say this is four , this is five ,...
how do we count the flowers ? so , this first choice , they go one , two , three , and then they do n't count this one and then they skip it and they go four , five , six , and then they skip this one again , and then they say seven , eight .
how do you cownt the to 20 ?
how do we count the flowers ? so , this first choice , they go one , two , three , and then they do n't count this one and then they skip it and they go four , five , six , and then they skip this one again , and then they say seven , eight . that 's not how you count flowers ! you 'd say this is four , this is five ,...
how do we count the flowers ? so , this first choice , they go one , two , three , and then they do n't count this one and then they skip it and they go four , five , six , and then they skip this one again , and then they say seven , eight .
what is the key to counting in order ?
how do we count the flowers ? so , this first choice , they go one , two , three , and then they do n't count this one and then they skip it and they go four , five , six , and then they skip this one again , and then they say seven , eight . that 's not how you count flowers ! you 'd say this is four , this is five ,...
it 's a lot of fun . count the flowers . type the missing numbers in the boxes .
is there an easier way to count in order ?
how do we count the flowers ? so , this first choice , they go one , two , three , and then they do n't count this one and then they skip it and they go four , five , six , and then they skip this one again , and then they say seven , eight . that 's not how you count flowers ! you 'd say this is four , this is five ,...
it 's a lot of fun . count the flowers . type the missing numbers in the boxes .
what is the easiest way to count in order ?
how do we count the flowers ? so , this first choice , they go one , two , three , and then they do n't count this one and then they skip it and they go four , five , six , and then they skip this one again , and then they say seven , eight . that 's not how you count flowers ! you 'd say this is four , this is five ,...
type the missing numbers in the boxes . this is flower number one , flower number two . just gon na type that right in there .
i really want to know the history of the number zero ?
how do we count the flowers ? so , this first choice , they go one , two , three , and then they do n't count this one and then they skip it and they go four , five , six , and then they skip this one again , and then they say seven , eight . that 's not how you count flowers ! you 'd say this is four , this is five ,...
it 's a lot of fun . count the flowers . type the missing numbers in the boxes .
so to count in order you have to count number by number not by spaces ?