### Prateek Asked :

25-09-2021
Electromagnetic Theory

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Q. The numerical aperture of a material with acceptance angle of 60 degree in water will be

A. 1.15

B. 2.15

C. 5.21

D. 1.52

### Submit Your Answer

Dapzoi

Commented on 2021-09-25 11:07:47 (IST)

Answer: A

Explanation: The numerical aperture is given by NA = n sin θa, where n is the refractive index. It is 1.33 for water medium. Given that the acceptance angle is 60, we get NA = 1.33 sin 60 = 1.15.