Question

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Question 2 0/1 point Athin oil slick (n-2.0) floats on water (n=1.33). A beam of white light strikes the oil at normal incidence from air. The only enhanced reflected wavelengths are 240 nm and 400 nm. What is the minimum thickness of the oil slick? Answer: 150 % (48) nm Question 3 0/1 point Three polarizers are placed in succession with their axes vertical, at 14° to the vertical, and at 90° to the vertical. What is the total fraction of incident unpolarized light that passes through all three filters? Answer: 0.06 x 10.028)

Answer 1

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The condition for constructive interferance is, 1 2nt = m + a 2. = -(1) -(2) + For red light: (2m+1) Pred 2not 2 For violet light: (2m'+1) Aviolet 2not 2 divide equation (1) with (2) (2m+1) Pred 2 - 1 (2m'+1) Violet 2 (2m+1) 2.red =1 (2m'+1) Aviolet (2m+1)_ Priolet (2m'+1) 400 240 1 4 Thus, 2m +1=1 m=0 Subdtitute in equation (1) (2m+1) Pred 2not 2 = hred 2 1 t= hed 4n (240 nm) 4(1.33) = 48 nm and 2m'+1=4 2m = 3 m'=1.5 Subdtitute in equation (2) (2m'+1) Aviolet 2not = 2 4 Enviolet 4. t= violet 4n. 4 (400 nm) 4(2.0) = 200 nm Thus, the minimum thickness is 200 nm