Question

When a light ray is incident on a prism at an angle of 45°, the minimum deviation is obtained. If refractive index of material of prism is `sqrt2`, then angle of prism will be ______.

`sin  pi/4=1/sqrt2, sin30^circ=cos60^circ=1/2`

Options

• 75°

• 30°

• 45°

• 60°

Answer 1

When a light ray is incident on a prism at an angle of 45°, the minimum deviation is obtained. If refractive index of material of prism is `sqrt2`, then angle of prism will be 60°.

Explanation:

`"i"=("A"+deltam)/2=45^circ`

`(sin45^circ)/(sin"A"/2)=sqrt2`

`therefore1/2=sin  "A"/2=sin30^circ`

`therefore"A"/2=30^circ`

∴ A = 60°