What should be the maximum acceptance angle at the aircore interface of an optical fibre if 1 n and 2 n are the refractive indices of the core and the cladding, respectively

What should be the maximum acceptance angle at the air–core interface of an optical fibre if n_(1) and n_(2) are the refractive indices of the core and the cladding, respectively

If refractive index of core & cladding are mu_(1)&mu_(2) respectively then :

In optical fibre is refractive index of core greater than cladding or smaller ?

If refractive index of core & cladding are mu_(1) & mu_(2) respectively then :

Numerical aperture of an optical fibre (w.r.t air) having core and cladding refractive indices n_(1) and n_(2) respectively is