90 In Fig. 33-71, two light rays pass from air through five layers of transparen
ID: 2035590 • Letter: 9
Question
90 In Fig. 33-71, two light rays pass from air through five layers of transparent plastic and then back into air. The layers have parallel interfaces and unknown thicknesses; their indexes of refraction are n 1.7, n2 1.6, n3 1.5, n4 1.4, and ns- 1.6. Ray b is incident at angle e, 200. Relative to a normal at the last interface, at what angle do (a) ray a and (b) ray b emerge? (Hin: Solving the problem algebraically can save time.) If the air at the left and right sides in the figure were, in- stead, glass with index of refraction 1.5, at what angle would (c) ray a and (d) ray b emerge? b Air n 2ms 4 n5 Air Fig. 33-71 Problem 90.Explanation / Answer
Given,
n1 = 1.7 ; n2 = 1.6 ; n3 = 1.5 ; n4 = 1.4 ; n5 = 1.6 ; theta-b = 20 deg
a)We see in the figure that ray a is perpendicular to the surface so no refraction will occur.
theta-a = 0 deg
b)since the ray enters from air, so n = 1 and when it leaves into air, n = 1 , so n = n7 = 1
theta-b = 20 deg
c)n = 1.5
this will remain zero, as stated in a
theta-a = 0 deg
d)In this case also, n0 = n7 = 1.5 so the angle will remain same as (b)
theta-b = 20 deg
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