Refer figure. Core has refractive index `mu_(1)=1.424`. The cladding refractive index `mu_(2)=1.39`. In such a case. Will the light beam propagate?

Options

A. Yes
B. No
C. Data given insufficient to decide
D. the beam propagation is not affected with refractive indices of fibre core and cladding.

Answer

A

Explanation

If `mu_(1)` is the refractiv e index of c ore of optical fibre, then
`mu_(1)=(sin 10^( o))/(sin7^(o))=(0.1736)/(0.1219)=1.424`
Critical angle at core and cladding surface in
`sin C=(mu_(2))/(mu_(1))=(1.39)/(1.424)=0.9761=sin 77^(@)27'`
`C=77^(@)7`'
The angle of incidence on core-cladding surface `= 90^(@)-7^(@)=83^(@)`, which is greater than critical single, hence beam will propagation through optical fibre.