Question

A small source of light is 4 m below the surface of water of refractive index 5/3. In order to cut off all the light, corning out of water surface, minimum diameter of the disc placed on the surface of water is

(a) 6 m 

(b) ∞

(c) 3 m 

(d) 4 m.

Answer 1

Correct option  (a) 6 m 

Explanation:

In order to cut of fall the light coming out of water surface, angle C should be equal to critical angle.