Question

A glass prism placed in a homogeneous transparent medium will deviate a light ray

A) always towards its base

B) always away from tis base

C) towards its base only if the medium has a refractive index smaller than that of glass

D) towards its base only if the medium has a refractive index greater than that of glass

I need to explain why the answer is what it is

Answer 1

According to snell's law, n1 sin i = n2 sin r , where n1 is refractive index of medium in which incident ray is traveling, n2 is refractive index of medium in which refracted ray is traveling, i is angle of incidence and r is angle of refraction.

For the given problem, light deviates towards the base if i > r => sin i > sin r => n1<n2.

Here, n1 is refractive index of the transparent medium in which prism is placed, n2 is refractive index of the prism(i.e. glass).

So, refractive index of the medium must have smaller refractive index than glass if light is being deviated towards the base.

So, option C is correct.