There is an equilateral prism of material of refractive index 1.5. Light ray is incident normally on its surface. What will be the angle of deviation of ray ?

Options

A. `15^(@)`
B. `30^(@)`
C. `45^(@)`
D. `60^(@)`

Answer

D

Explanation

Following is the ray diagram for the given situation:

Light ray incident normal to the surface pass un-deviated and is incident on the next surface at an angle `60^(@)` which is greater than critical angle. Hence, light ray from this surface is internally reflected and is incident normal on the next surface to pass un-deviated. So final angle of deviation is `60^(@)` as shown in figure. Hence, option (d) is correct.