A ray of light passes through an equilateral prism such that the angle of incidence is equal to the angle of emergence and each one is equal to 3/4 times the angle of prism. The angle of deviation is

Options

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

Answer

D

Explanation

Angle of incidence (i) + Angle of emergence (e) = Angle of prism (A) + Angle of deviation(`delta`)
`delta=i+e-A`
`implies3/4 xx60 + ¾ xx60 – 60= delta`
`therefore delta=90-60=30^@`