Question

A ray PQ is incident normally on the face AB of a triangular prism of refracting angle 60° as shown in figure. The prism is made of a transparent material of refractive index `2/sqrt(3)`. Trace the path of the ray as it passes through the prism. Calculate the angle of emergence and the angle of deviation.

Answer 1

Given: ∠A = 60°, ∠i = 0°

At M: Sin C = `1/μ = sqrt(3)/2` = sin 60°

∴ C = 60°

So the ray PM after refraction from the face AC grazes along AC.

∴ ∠C = 90°

From ∠i + ∠C = ∠A + ∠δ

Or 0° + 90° = 60° + ∠δ

∴ δ = 90° – 60° = 30°