Question

A light ray is incident normally on the face AB of a right-angled prism ABC (μ= 1.50) as shown in figure (18 E9). What is the largest angle ϕ  for which the light ray is totally reflected at the surface AC ?

Answer 1

Let θ_c be the critical angle for the glass

So, the largest angle for which light is totally reflected at the surface is cos^–1(2/3).