Question

A ray of light is incident normally on one face of an equilateral glass prism of refractive index μ. When the prism is completely immersed in a transparent medium, it is observed that the emergent ray just grazes the adjacent face. Find the refractive index of the medium.

Answer 1

For a prism we have

r₁ + r₂ = A

Here r₁ = 0

⇒ r₂ = A

Applying Snell's law

µ sin r₂ = µ_m sin 90°

µ sinA = µ_m

⇒ µ sin60 = µ_m

⇒ `mu_m = sqrt3/2 mu`