Calculate the N.A of a step index fibre having n1=1.48 and n2=1.46. What is the maximum entrance angle ψmax for this fibre if the outer medium is air with n1=1.0?
Given
n1=1.48
n2=1.46
We know that numerical aperture,
Sinψ = (n12- n22)½= (1.482- 1.462)½
=0.2425
ψmax= sin-1(0.2425)
= 14.03°