Optics 2 Question 17

17. A transparent slab of thickness d has a refractive index n(z) that increases with z. Here, z is the vertical distance inside the slab, measured from the top. The slab is placed between two media with uniform refractive indices n1 and n2(>n1), as shown in the figure. A ray of light is incident with angle θi from medium 1 and emerges in medium 2 with refraction angle θf with a lateral displacement l.

(2016 Main)

Which of the following statement(s) is (are) true? (a) l is independent on n(z)

(b) n1sinθi=(n2n1)sinθf

(c) n1sinθi=n2sinθf

(d) l is independent of n2

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Answer:

Correct Answer: 17. (a, c, d)

Solution:

  1. From Snell’s law,

nsinθ= constant

n1sinθi=n2sinθf

Further, l will depend on n1 and n(z). But it will be independent of n2.



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