A ray of light passes through an equilateral prism (refractive index `1.5`) such that angle of incidence is equal to angle of emergence and the latter is equal to `3//4 th` of the angle of prism. Calculate the angle of deviation.

Options

A. `45^(@)`
B. `39^(@)`
C. `20^(@)`
D. `30^(@)`

Answer

D

Explanation

`i_(1)=i_(2)=(3)/(4)A`
As `A+delta=i_(1)+i_(2)`
`therefore delta=i_(1)+i_(2) -A=(3)/(4)A+(3)/(4)A-A=(A)/(2)=(60^(@))/(2)=30^(@)`