Q. A prism is made of glass of unknown refractive index. A parallel beam of light is incident on a face of the prism. The angle of minimum deviation is measured to be 40°.What is the refractive index of the material of the prism? The refracting angle of the prism is 60°.If the prism is placed in water (refractive index 1.33), predict the new angle of minimum deviation f a parallel beam of light.

Answer

The Angle of minimum deviation δm =40°

The Angle of the prism A=60°

The Refractive index of water F=1.33

Refractive index of the material of the prism=μ'

An Angle of deviation is related to refractive index μ' as:

Consequently the refractive index of the material of the prismis 1.532

While the prism is placed in water let δ'm be the new angle of minimum deviation for the same prism.

A refractive index of glass with respect to water is given by the relation:

Therefore the new minimum angle of deviation is 10.32°.