Question

(i) On entering in a medium from air, the speed of light becomes half of its value in air. Find the refractive index of that medium with respect to air?

(ii) A glass slab made of a material of refractive index n1 is kept in a medium of refractive index n2. A light ray is incident on the slab. Draw the path of the rays of light emerging from the glass slab, if

(i) n1> n2 (ii) n1 = n2 (iii) n1< n2

Answer 1

(i) Refractive Index of a medium (µ) = Velocity of light in vacuum / Velocity of light in the medium. Let the velocity of light in vacuum be v1 and velocity of light in the medium be v2. v1 /2 = v2.

Hence µ = v1 / v2. = v1 / (v1 /2 ). = 2

(ii) (a) The ray moves towards the normal.

(b) The ray moves undeviated.

(c) The ray moves away from the normal.