Question

Prove that NA of fibre does not depend upon the dimension of the fibre.

Answer 1

Numerical Aperture is defined as the Sine of half  of the angle of fibre’s light acceptance cone.  i.e. NA= Sin θa where θa, is called acceptance cone angle.

From the formula it is clear enough that it doesn't depends on the dimension of the fibre but on the value of theta. You know that numerical aperture of a fibre is that light entering in the course of semi Vertical angle I suffix and which only propagate through the fibre that is it is a light gathering capacity of an optical fibre.