1059_Physics ProblemsTechnical Physics

1059_Physics ProblemsTechnical Physics - 400 P37.56...

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400 Interference of Light Waves P37.56 At entrance, 1 00 30 0 1 38 2 .s i n. i n °= θθ 2 21 2 . Call t the unknown thickness. Then cos . 21 2 t a a t = ° cos . 21 2 tan . 21 2 c t ct tan . 21 2 sin θ 1 2 = b c bt ° 22 1 23 0 0 t a n.s i The net shift for the second ray, including the phase reversal on reflection of the first, is FIG. P37.56 2 2 an b −− λ where the factor n accounts for the shorter wavelength in the film. For constructive interference, we require 2 2 an b m −− = . The minimum thickness will be given by 2 2 0 an b . 2 21 2 1 0 0 =− = ° −° ° an b nt t cos . t a n. s i a f 590 2 1 38 21 2 2 21 2 30 0 2 57 nm 2 = × ° ° F H G I K J = . cos . t a i . tt t = 115 nm P37.57 The shift between the two reflected waves is δ 2 2 na b where a and b are as shown in the ray diagram, n is the index of refraction, and the term 2 is due to phase reversal at the top surface. For constructive interference, δλ = m where
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This note was uploaded on 12/14/2011 for the course PHY 203 taught by Professor Staff during the Fall '11 term at Indiana State University .

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