Question

The refractive indices of the core and cladding materials of an optical fibre are 1.51 and 1.39 respectively. calculate the numerical aperture and light gathering capacity of the fibre.

Answer 1

Numerical Aperture =
$\sqrt{ {n1}^{2} - {n2}^{2} }$
Numerical aperture =
$\sqrt{ {1.51}^{2} - {1.39}^{2} }$
Numerical aperture =
$\sqrt{0.348}$
Numerical apeture or light gathering capacity = 0.1211