Question

Calculate the numerical aperture of an optical fibre whose core and cladding are made of materials of refractive index 1.6 and 1.5 respectively.

(a) 0.55677

(b) 55.77

(c) 0.2458

(d) 0.647852

I got this question in an interview for job.

The origin of the question is Optical Fibre topic in section Laser of Engineering Physics II

Answer 1

The correct answer is (a) 0.55677

To elaborate: Numerical aperture = \(\sqrt{n1^2-n2^2}\)

Numerical aperture = 0.55677.