Answer to Question #117802 in Optics for Nakul gowda an

Question

The angle of acceptance of an optical fibre is 30 degree when kept in air. find the angle of acceptance when it is in a medium of refractive index 1.33

Answer 1

Acceptance angle= $\sin^{-1}(\frac{NA}{n_o})=\sin^{-1}(\frac{n_1^2-n_2^2}{n_o})$

in air $n_o=1$

$30^o=\sin^{-1}(NA)$

NA=0.5

acceptance angle when refractive index of medium is 1.33

new acceptance angle = $\sin^{-1}(\frac{0.5}{1.33})=\sin^{-1}0.37$ =$21.7^o$