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25-09-2021 Electromagnetic Theory

Q. The refractive index is 2.33 and the critical angle is 350. Find the numerical aperture.

A. 2
B. 1.9
C. 2.33
D. 12


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Dapzoi Verified
Commented on 2021-09-25 11:08:11 (IST)
Answer: B

Explanation: The numerical aperture is given by NA = n cos θc, where θc is the critical angle and n is the refractive index. On substituting for n = 2.33 and θc = 35, we get NA = 2.33 cos 35 = 1.9(no unit).