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Doppler effect
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•Effect similar in light and sound
–Waves compressed with source moving toward you
•Sound pitch is higher, light wavelength is smaller (bluer)
–Waves stretched with source moving away from you
•Sound pitch is lower, light wavelength is longer (redder)
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•v  =  velocity of source
•c  =  velocity of light (or sound)
•l  =  apparent wavelength of light
•lo =  original wavelength of light