The indices of refraction for red, green, and violet light in glass are nred = 1.520, ngreen = 1.526, and nviolet = 1.538. When a ray of light passes through a transparent slab of glass, the emergent ray is parallel to the incident ray, but can be displaced relative to it. For light passing through a glass slab that is surrounded by air, which color is displaced the most?

(a) All colors are displaced equally.

(b) Red

(c) Green

(d) Violet

(d) Violet

Explanation:

The formula for lateral displacement = t sin (i - r) / cos r

where t is thickness of slab, i is angle of incidence, r is angle of refraction

refractive index = sin i / sin r

if refractive index is high, for given i, angle of r will be less

i - r will be more, hence sin (i - r) will be more

cos r will be less (larger the angle, lesser will be its cos value)

sin (i - r) / cos r will be more

lateral displacement will be more.

hence higher refractive index results into greater displacement.

So violet ray will undergo maximum displacement.