90 In Fig. 33-71, two light rays pass from air through five layers of transparen

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 ni 17, n,-1.6, n,-15, n4-1.4, and n,- 1.6. Ray b is incident at angle 0, 20o. Relative to a normal at the last interface, at what angle do (a) ray a and (b) ray b emerge? (Hint: 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 n5 Air 4 Fig. 33-71 Problem 90.

Explanation / Answer

now for both sides of the layers we have refractive index air (n =1)

we get

n1sin(theta1)=n2sin(theta2) =n7 sin(theta7)

part A:

here the incident ray is perpendicular to the surface

for whcih there will be no refraction

so that theta1=theta7=0 degrees
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b) Since the index of n1=n7 for ray b,

then theta1=theta7=20 degrees

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c) Even when changed with glass or any refractive index (1.5)

incident ray is still perpendicular

so that theta1=theta7=0 degrees

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d) Since the index of n1=n7 for ray b,

then theta1=theta7=20 degrees

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