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.