A ray of light passes through an equilateral glass prism in such a manner that the angle of incidence is equal to the angle of emergence and each of these angles is equal to 3/4 of the angle of the prism. The angle of deviation is

Options

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

Answer

D

Explanation

Given, angle of prism, `A=60^(@)`
Angle of incidence, i = Angle of emergence, e
`e=(3)/(4)A`
As, `delta=i+e-A=e+e-A=2e-A`
`=2((3)/(4))A-A=(A)/(2)=(60^(@))/(2)=30^(@)`