Light and Optics
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| electromagnetic wave | travelling oscillation of an electric and a magnetic field which are perpendicular to each other and the direction of propagation is perpendicular to both fields; generated by acceleration of electric charge
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| speed of electromagnetic wave | c = E/B
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| visible light | wavelength range from 390 to 700 nm (shorter wavelength is violet and longer wavelength is red)
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| electromagnetic spectrum (large to small wavelength) | long waves > radio waves > infrared > visible light > ultraviolet > x-rays > gamma rays
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| index of refraction | n = c/v
constant specific to a medium that helps describe the speed of light in that medium, always greater than 1, the larger the n - the slower light moves in that medium
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| n for water (refractive index) | 1.3
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| n for glass (refractive index) | 1.5
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| light | made up of photons that each represent an EM wave, has a dual nature bc it can act as a wave and a particle, approximated as a ray moving in a straight line
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| wave theory applied to light | propagation properties of light - reflection or refraction at the interference of 2 media
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| particle theory applied to light | energy transformation properties
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| angle of incidence | angle at which light ray strikes the interface, is equal to the angle of reflection (bc collision of photons against the interface is completely elastic)
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| angle of refraction | angle at which the light refracts at the interface, given by Snell's law
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| Snell's law | n1*sin(theta1) = n2*sin(theta2) where 1 and 2 specify their specific media
**angle of incidence/refraction not specified bc it makes no difference if light is moving from 1 to 2 or 2 to 1
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| easier way to think about the path of light in different mediums | light wants to travel btw any two points in the shortest possible path for light in terms of TIME - whichever medium that light is faster, it will want to "spend more time there" so the light will bend in the same direction in the interface
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| when light crosses into a new medium, the ____ remains the same, and the ____ changes | frequency same, wavelength changes
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| eqn for the energy of single photon | E = hf (h is Planck's constant, f is frequency)
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| total internal reflection | if the angle of incidence is large enough, the entire amount of photons will be reflected at the angle of reflection and NONE will refract, occurs at the critical angle
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| critical angle | = sin-1(n2/n1)
(inverse sin of the ratio of n2 to n1)
derived from Snell's law
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| chromatic dispersion | where white light (which is made up of all frequencies in the visible spectrum) is split by a prism
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| diffraction | when a wave moves through a small opening and bends around the corner of the opening, only significant if the size of the opening is on the order of the wavelength or smaller (smaller the hole, the greater the spreading)
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| constructive interference with diffracted waves result in.. | bright bands
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| destructive interference with diffracted waves result in | dark bands
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| concave mirror makes what kind of image? | positive, real, inverted EXCEPT when object is within focal distance, when they will make negative, virtual upright images
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| convex mirror makes what kind of image? | negative, virtual, upright
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| converging lens makes what kind of image? | positive, real, inverted EXCEPT when object is within focal distance, when they will make negative, virtual upright images
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| diverging lens makes what kind of image | negative, virtual, upright
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| objects are always positive when.. | they are in front of a lens or mirror
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| objects are always negative when.. | they are behind a lens or mirror
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| which side of a lens/mirror is positive? | wherever the eye is - focal point and images here are real and inverted
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| which side of lens/mirror is negative? | the opposite side of the eye - focal point and images are virtual and upright
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| Power of lens | P = 1/f = 1/dimage + 1/dobject
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| magnification of lens | M = -dimage/dobject = himage/hobject
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| focal point of mirror | fmirror = 1/2*r
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| lateral magnification of two lens system | M = m1*m2
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| effective power of two lens system | Peff = P1 + P2
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| focal point | the single point where light from horizontal rays is reflected by concave mirrors (or refracted by converging lenses) is focused and reflected outward from convex mirrors and diverging lens
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| focal length | the distance that separates the mirror or lens from the focal point
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| which wavelengths are diffracted the most? | the longer the wavelength, the more it is diffracted
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| interference | when the path length traveled by light rays differs and creates high and low intensity bands due to constructive and destructive interference.
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| (chromatic dispersion) shorter wavelengths will bend more or less? | shorter wavelengths bend more
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| why does chromatic dispersion occur? | index of refraction for shorter wavelengths is greater than longer wavelengths in a given medium
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| (chromatic disperision) longer wavelengths will have greater or smaller angles of refraction when going from medium of lower n to higher n? | greater
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| focal point of plane mirror | infinite
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| focal point of concave mirror is positive or negative? | positive
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