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The rods are good for night vision, peripheral vision, and motion changes, while the cones are responsible for central vision and color. | https://openstax.org/books/college-physics-2e/pages/26-section-summary |
We perceive many hues, from light having mixtures of wavelengths. | https://openstax.org/books/college-physics-2e/pages/26-section-summary |
A simplified theory of color vision states that there are three primary colors, which correspond to the three types of cones, and that various combinations of the primary colors produce all the hues. | https://openstax.org/books/college-physics-2e/pages/26-section-summary |
The true color of an object is related to its relative absorption of various wavelengths of light. The color of a light source is related to the wavelengths it produces. | https://openstax.org/books/college-physics-2e/pages/26-section-summary |
Color constancy is the ability of the eye-brain system to discern the true color of an object illuminated by various light sources. | https://openstax.org/books/college-physics-2e/pages/26-section-summary |
The retinex theory of color vision explains color constancy by postulating the existence of three retinexes or image systems, associated with the three types of cones that are compared to obtain sophisticated information. | https://openstax.org/books/college-physics-2e/pages/26-section-summary |
The microscope is a multiple-element system having more than a single lens or mirror. | https://openstax.org/books/college-physics-2e/pages/26-section-summary |
Many optical devices contain more than a single lens or mirror. These are analysed by considering each element sequentially. The image formed by the first is the object for the second, and so on. The same ray tracing and thin lens techniques apply to each lens element. | https://openstax.org/books/college-physics-2e/pages/26-section-summary |
The overall magnification of a multiple-element system is the product of the magnifications of its individual elements. For a two-element system with an objective and an eyepiece, this ism=mome,m=mome,wheremomois the magnification of the objective andmemeis the magnification of the eyepiece, such as for a microscope. | https://openstax.org/books/college-physics-2e/pages/26-section-summary |
Microscopes are instruments for allowing us to see detail we would not be able to see with the unaided eye and consist of a range of components. | https://openstax.org/books/college-physics-2e/pages/26-section-summary |
The eyepiece and objective contribute to the magnification. The numerical aperture(NA)(NA)of an objective is given byNA=nsinαNA=nsinαwherennis the refractive index andααthe angle of acceptance. | https://openstax.org/books/college-physics-2e/pages/26-section-summary |
Immersion techniques are often used to improve the light gathering ability of microscopes. The specimen is illuminated by transmitted, scattered or reflected light though a condenser. | https://openstax.org/books/college-physics-2e/pages/26-section-summary |
Thef/#f/#describes the light gathering ability of a lens. It is given byf/#=fDâ12NA.f/#=fDâ12NA. | https://openstax.org/books/college-physics-2e/pages/26-section-summary |
Simple telescopes can be made with two lenses. They are used for viewing objects at large distances and utilize the entire range of the electromagnetic spectrum. | https://openstax.org/books/college-physics-2e/pages/26-section-summary |
The angular magnification M for a telescope is given byM=θâ²Î¸=âfofe,M=θâ²Î¸=âfofe,whereθθis the angle subtended by an object viewed by the unaided eye,θâ²Î¸â²is the angle subtended by a magnified image, andfofoandfefeare the focal lengths of the objective and the eyepiece. | https://openstax.org/books/college-physics-2e/pages/26-section-summary |
Aberrations or image distortions can arise due to the finite thickness of optical instruments, imperfections in the optical components, and limitations on the ways in which the components are used. | https://openstax.org/books/college-physics-2e/pages/26-section-summary |
The means for correcting aberrations range from better components to computational techniques. | https://openstax.org/books/college-physics-2e/pages/26-section-summary |
axis of a polarizing filter : the direction along which the filter passes the electric field of an EM wave | https://openstax.org/books/college-physics-2e/pages/27-glossary |
birefringent : crystals that split an unpolarized beam of light into two beams | https://openstax.org/books/college-physics-2e/pages/27-glossary |
Brewsterâs angle : θb=tanâ1n2n1,θb=tanâ1n2n1,wheren2n2is the index of refraction of the medium from which the light is reflected andn1n1is the index of refraction of the medium in which the reflected light travels | https://openstax.org/books/college-physics-2e/pages/27-glossary |
Brewsterâs law : tanθb=n2n1tanθb=n2n1, wheren1n1is the medium in which the incident and reflected light travel andn2n2is the index of refraction of the medium that forms the interface that reflects the light | https://openstax.org/books/college-physics-2e/pages/27-glossary |
coherent : waves are in phase or have a definite phase relationship | https://openstax.org/books/college-physics-2e/pages/27-glossary |
confocal microscopes : microscopes that use the extended focal region to obtain three-dimensional images rather than two-dimensional images | https://openstax.org/books/college-physics-2e/pages/27-glossary |
constructive interference for a diffraction grating : occurs when the conditiondsinθ=mλ(form=0,1,â1,2,â2,â¦)dsinθ=mλ(form=0,1,â1,2,â2,â¦)is satisfied, whereddis the distance between slits in the grating,λλis the wavelength of light, andmmis the order of the maximum | https://openstax.org/books/college-physics-2e/pages/27-glossary |
constructive interference for a double slit : the path length difference must be an integral multiple of the wavelength | https://openstax.org/books/college-physics-2e/pages/27-glossary |
contrast : the difference in intensity between objects and the background on which they are observed | https://openstax.org/books/college-physics-2e/pages/27-glossary |
destructive interference for a double slit : the path length difference must be a half-integral multiple of the wavelength | https://openstax.org/books/college-physics-2e/pages/27-glossary |
destructive interference for a single slit : occurs whenDsinθ=mλ,(form=1,â1,2,â2,3,â¦)Dsinθ=mλ,(form=1,â1,2,â2,3,â¦), whereDDis the slit width,λλis the lightâs wavelength,θθis the angle relative to the original direction of the light, andmmis the order of the minimum | https://openstax.org/books/college-physics-2e/pages/27-glossary |
diffraction : the bending of a wave around the edges of an opening or an obstacle | https://openstax.org/books/college-physics-2e/pages/27-glossary |
diffraction grating : a large number of evenly spaced parallel slits | https://openstax.org/books/college-physics-2e/pages/27-glossary |
direction of polarization : the direction parallel to the electric field for EM waves | https://openstax.org/books/college-physics-2e/pages/27-glossary |
horizontally polarized : the oscillations are in a horizontal plane | https://openstax.org/books/college-physics-2e/pages/27-glossary |
Huygensâs principle : every point on a wavefront is a source of wavelets that spread out in the forward direction at the same speed as the wave itself. The new wavefront is a line tangent to all of the wavelets | https://openstax.org/books/college-physics-2e/pages/27-glossary |
incoherent : waves have random phase relationships | https://openstax.org/books/college-physics-2e/pages/27-glossary |
interference microscopes : microscopes that enhance contrast between objects and background by superimposing a reference beam of light upon the light emerging from the sample | https://openstax.org/books/college-physics-2e/pages/27-glossary |
optically active : substances that rotate the plane of polarization of light passing through them | https://openstax.org/books/college-physics-2e/pages/27-glossary |
order : the integermmused in the equations for constructive and destructive interference for a double slit | https://openstax.org/books/college-physics-2e/pages/27-glossary |
phase-contrast microscope : microscope utilizing wave interference and differences in phases to enhance contrast | https://openstax.org/books/college-physics-2e/pages/27-glossary |
polarization : the attribute that wave oscillations have a definite direction relative to the direction of propagation of the wave | https://openstax.org/books/college-physics-2e/pages/27-glossary |
polarization microscope : microscope that enhances contrast by utilizing a wave characteristic of light, useful for objects that are optically active | https://openstax.org/books/college-physics-2e/pages/27-glossary |
polarized : waves having the electric and magnetic field oscillations in a definite direction | https://openstax.org/books/college-physics-2e/pages/27-glossary |
Rayleigh criterion : two images are just resolvable when the center of the diffraction pattern of one is directly over the first minimum of the diffraction pattern of the other | https://openstax.org/books/college-physics-2e/pages/27-glossary |
reflected light that is completely polarized : light reflected at the angle of reflectionθbθb, known as Brewsterâs angle | https://openstax.org/books/college-physics-2e/pages/27-glossary |
thin film interference : interference between light reflected from different surfaces of a thin film | https://openstax.org/books/college-physics-2e/pages/27-glossary |
ultraviolet (UV) microscopes : microscopes constructed with special lenses that transmit UV rays and utilize photographic or electronic techniques to record images | https://openstax.org/books/college-physics-2e/pages/27-glossary |
unpolarized : waves that are randomly polarized | https://openstax.org/books/college-physics-2e/pages/27-glossary |
vertically polarized : the oscillations are in a vertical plane | https://openstax.org/books/college-physics-2e/pages/27-glossary |
wavelength in a medium : λn=λ/nλn=λ/n, whereλλis the wavelength in vacuum, andnnis the index of refraction of the medium | https://openstax.org/books/college-physics-2e/pages/27-glossary |
Wave optics is the branch of optics that must be used when light interacts with small objects or whenever the wave characteristics of light are considered. | https://openstax.org/books/college-physics-2e/pages/27-section-summary |
Wave characteristics are those associated with interference and diffraction. | https://openstax.org/books/college-physics-2e/pages/27-section-summary |
Visible light is the type of electromagnetic wave to which our eyes respond and has a wavelength in the range of 380 to 760 nm. | https://openstax.org/books/college-physics-2e/pages/27-section-summary |
Like all EM waves, the following relationship is valid in vacuum:c=fλc=fλ, wherec=3Ã108m/sc=3Ã108m/sis the speed of light,ffis the frequency of the electromagnetic wave, andλλis its wavelength in vacuum. | https://openstax.org/books/college-physics-2e/pages/27-section-summary |
The wavelengthλnλnof light in a medium with index of refractionnnisλn=λ/nλn=λ/n. Its frequency is the same as in vacuum. | https://openstax.org/books/college-physics-2e/pages/27-section-summary |
An accurate technique for determining how and where waves propagate is given by Huygensâs principle: Every point on a wavefront is a source of wavelets that spread out in the forward direction at the same speed as the wave itself. The new wavefront is a line tangent to all of the wavelets. | https://openstax.org/books/college-physics-2e/pages/27-section-summary |
Diffraction is the bending of a wave around the edges of an opening or other obstacle. | https://openstax.org/books/college-physics-2e/pages/27-section-summary |
Youngâs double slit experiment gave definitive proof of the wave character of light. | https://openstax.org/books/college-physics-2e/pages/27-section-summary |
An interference pattern is obtained by the superposition of light from two slits. | https://openstax.org/books/college-physics-2e/pages/27-section-summary |
There is constructive interference whendsinθ=mλ(form=0,1,â1,2,â2,â¦)dsinθ=mλ(form=0,1,â1,2,â2,â¦), whereddis the distance between the slits,θθis the angle relative to the incident direction, andmmis the order of the interference. | https://openstax.org/books/college-physics-2e/pages/27-section-summary |
There is destructive interference whendsinθ=m+12λ(form=0,1,â1,2,â2,â¦)dsinθ=m+12λ(form=0,1,â1,2,â2,â¦). | https://openstax.org/books/college-physics-2e/pages/27-section-summary |
A diffraction grating is a large collection of evenly spaced parallel slits that produces an interference pattern similar to but sharper than that of a double slit. | https://openstax.org/books/college-physics-2e/pages/27-section-summary |
There is constructive interference for a diffraction grating whendsinθ=mλ(form=0,1,â1,2,â2,â¦)dsinθ=mλ(form=0,1,â1,2,â2,â¦), whereddis the distance between slits in the grating,λλis the wavelength of light, andmmis the order of the maximum. | https://openstax.org/books/college-physics-2e/pages/27-section-summary |
A single slit produces an interference pattern characterized by a broad central maximum with narrower and dimmer maxima to the sides. | https://openstax.org/books/college-physics-2e/pages/27-section-summary |
There is destructive interference for a single slit whenDsinθ=mλ,(form=1,â1,2,â2,3,â¦)Dsinθ=mλ,(form=1,â1,2,â2,3,â¦), whereDDis the slit width,λλis the lightâs wavelength,θθis the angle relative to the original direction of the light, andmmis the order of the minimum. Note that there is nom=0m=0mini... | https://openstax.org/books/college-physics-2e/pages/27-section-summary |
Diffraction limits resolution. | https://openstax.org/books/college-physics-2e/pages/27-section-summary |
For a circular aperture, lens, or mirror, the Rayleigh criterion states that two images are just resolvable when the center of the diffraction pattern of one is directly over the first minimum of the diffraction pattern of the other. | https://openstax.org/books/college-physics-2e/pages/27-section-summary |
This occurs for two point objects separated by the angleθ=1.22λDθ=1.22λD, whereλλis the wavelength of light (or other electromagnetic radiation) andDDis the diameter of the aperture, lens, mirror, etc. This equation also gives the angular spreading of a source of light having a diameterDD. | https://openstax.org/books/college-physics-2e/pages/27-section-summary |
Thin film interference occurs between the light reflected from the top and bottom surfaces of a film. In addition to the path length difference, there can be a phase change. | https://openstax.org/books/college-physics-2e/pages/27-section-summary |
When light reflects from a medium having an index of refraction greater than that of the medium in which it is traveling, a180º180ºphase change (or aλ/2λ/2shift) occurs. | https://openstax.org/books/college-physics-2e/pages/27-section-summary |
Polarization is the attribute that wave oscillations have a definite direction relative to the direction of propagation of the wave. | https://openstax.org/books/college-physics-2e/pages/27-section-summary |
EM waves are transverse waves that may be polarized. | https://openstax.org/books/college-physics-2e/pages/27-section-summary |
The direction of polarization is defined to be the direction parallel to the electric field of the EM wave. | https://openstax.org/books/college-physics-2e/pages/27-section-summary |
Unpolarized light is composed of many rays having random polarization directions. | https://openstax.org/books/college-physics-2e/pages/27-section-summary |
Light can be polarized by passing it through a polarizing filter or other polarizing material. The intensityIIof polarized light after passing through a polarizing filter isI=I0cos2θ,I=I0cos2θ,whereI0I0is the original intensity andθθis the angle between the direction of polarization and the axis of the filter. | https://openstax.org/books/college-physics-2e/pages/27-section-summary |
Polarization is also produced by reflection. | https://openstax.org/books/college-physics-2e/pages/27-section-summary |
Brewsterâs law states that reflected light will be completely polarized at the angle of reflectionθbθb, known as Brewsterâs angle, given by a statement known as Brewsterâs law:tanθb=n2n1tanθb=n2n1, wheren1n1is the medium in which the incident and reflected light travel andn2n2is the index of refraction of the... | https://openstax.org/books/college-physics-2e/pages/27-section-summary |
Polarization can also be produced by scattering. | https://openstax.org/books/college-physics-2e/pages/27-section-summary |
There are a number of types of optically active substances that rotate the direction of polarization of light passing through them. | https://openstax.org/books/college-physics-2e/pages/27-section-summary |
To improve microscope images, various techniques utilizing the wave characteristics of light have been developed. Many of these enhance contrast with interference effects. | https://openstax.org/books/college-physics-2e/pages/27-section-summary |
classical velocity addition : the method of adding velocities whenv<<cv<<c; velocities add like regular numbers in one-dimensional motion:u=v+uâ²u=v+uâ², wherevvis the velocity between two observers,uuis the velocity of an object relative to one observer, anduâ²uâ²is the velocity relative to the other observer | https://openstax.org/books/college-physics-2e/pages/28-glossary |
first postulate of special relativity : the idea that the laws of physics are the same and can be stated in their simplest form in all inertial frames of reference | https://openstax.org/books/college-physics-2e/pages/28-glossary |
inertial frame of reference : a reference frame in which a body at rest remains at rest and a body in motion moves at a constant speed in a straight line unless acted on by an outside force | https://openstax.org/books/college-physics-2e/pages/28-glossary |
length contraction : LL, the shortening of the measured length of an object moving relative to the observerâs frame:L=L01âv2c2=L0γL=L01âv2c2=L0γ | https://openstax.org/books/college-physics-2e/pages/28-glossary |
Michelson-Morley experiment : an investigation performed in 1887 that proved that the speed of light in a vacuum is the same in all frames of reference from which it is viewed | https://openstax.org/books/college-physics-2e/pages/28-glossary |
proper length : L0L0; the distance between two points measured by an observer who is at rest relative to both of the points; Earth-bound observers measure proper length when measuring the distance between two points that are stationary relative to the Earth | https://openstax.org/books/college-physics-2e/pages/28-glossary |
proper time : Ît0Ît0. the time measured by an observer at rest relative to the event being observed:Ît=Ît01âv2c2=γÎt0Ît=Ît01âv2c2=γÎt0, whereγ=11âv2c2γ=11âv2c2 | https://openstax.org/books/college-physics-2e/pages/28-glossary |
relativistic Doppler effects : a change in wavelength of radiation that is moving relative to the observer; the wavelength of the radiation is longer (called a red shift) than that emitted by the source when the source moves away from the observer and shorter (called a blue shift) when the source moves toward the obser... | https://openstax.org/books/college-physics-2e/pages/28-glossary |
relativistic kinetic energy : the kinetic energy of an object moving at relativistic speeds:KErel=γâ1mc2KErel=γâ1mc2, whereγ=11âv2c2γ=11âv2c2 | https://openstax.org/books/college-physics-2e/pages/28-glossary |
relativistic momentum : pp, the momentum of an object moving at relativistic velocity;p=γmup=γmu, wheremmis the rest mass of the object,uuis its velocity relative to an observer, and the relativistic factorγ=11âu2c2γ=11âu2c2 | https://openstax.org/books/college-physics-2e/pages/28-glossary |
relativistic velocity addition : the method of adding velocities of an object moving at a relativistic speed:u=v+uâ²1+vuâ²c2u=v+uâ²1+vuâ²c2, wherevvis the relative velocity between two observers,uuis the velocity of an object relative to one observer, anduâ²uâ²is the velocity relative to the other observer | https://openstax.org/books/college-physics-2e/pages/28-glossary |
relativity : the study of how different observers measure the same event | https://openstax.org/books/college-physics-2e/pages/28-glossary |
rest energy : the energy stored in an object at rest:E0=mc2E0=mc2 | https://openstax.org/books/college-physics-2e/pages/28-glossary |
rest mass : the mass of an object as measured by a person at rest relative to the object | https://openstax.org/books/college-physics-2e/pages/28-glossary |
second postulate of special relativity : the idea that the speed of lightccis a constant, independent of the source | https://openstax.org/books/college-physics-2e/pages/28-glossary |
special relativity : the theory that, in an inertial frame of reference, the motion of an object is relative to the frame from which it is viewed or measured | https://openstax.org/books/college-physics-2e/pages/28-glossary |
time dilation : the phenomenon of time passing slower to an observer who is moving relative to another observer | https://openstax.org/books/college-physics-2e/pages/28-glossary |
total energy : defined asE=γmc2E=γmc2, whereγ=11âv2c2γ=11âv2c2 | https://openstax.org/books/college-physics-2e/pages/28-glossary |
twin paradox : this asks why a twin traveling at a relativistic speed away and then back towards the Earth ages less than the Earth-bound twin. The premise to the paradox is faulty because the traveling twin is accelerating, and special relativity does not apply to accelerating frames of reference | https://openstax.org/books/college-physics-2e/pages/28-glossary |
Relativity is the study of how different observers measure the same event. | https://openstax.org/books/college-physics-2e/pages/28-section-summary |
Modern relativity is divided into two parts. Special relativity deals with observers who are in uniform (unaccelerated) motion, whereas general relativity includes accelerated relative motion and gravity. Modern relativity is correct in all circumstances and, in the limit of low velocity and weak gravitation, gives the... | https://openstax.org/books/college-physics-2e/pages/28-section-summary |
An inertial frame of reference is a reference frame in which a body at rest remains at rest and a body in motion moves at a constant speed in a straight line unless acted on by an outside force. | https://openstax.org/books/college-physics-2e/pages/28-section-summary |
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