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 .

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