Question

A prism of refractive index `sqrt2` and refracting angle A produces minimum deviation δ_m of a ray on one face at an angle of incidence 45°, The values of A and δ_m are, respectively ______.

Options

• 45°, 45°

• 45°, 60°

• 60°, 30°

• 60°, 45°

Answer 1

A prism of refractive index `sqrt2` and refracting angle A produces minimum deviation δ_m of a ray on one face at an angle of incidence 45°, The values of A and δ_m are, respectively 60°, 30°.

Explanation:

For minimum deviation, i = e, r = r'

r + r' = A

⇒ 2r = A

By Snell's law, `sin45^circ = sqrt2sinr`

sin r = `1/2`

⇒ r = 30°

∴ A = 2(30°) = 60°

Minimum deviation,

δ_m = i + i – A

= 90° – 60°

= 30°