Total internal reflection at hypotenuse in 45-45-90 prism

[kthejohnster]

Homework Statement

A 45,45,90 glass triangular prism (n=1.52) is surrounded by air. If a light ray comes into one of the legs (not hypotenuse) at a right angle which legs have total internal reflection?

Homework Equations

n_1sinx_i=n_2sinx_r

The Attempt at a Solution

i figured out that the light ray on the first incident leg transmits light to hypotenuse at but am getting confused on how to get the reflection angle at the hypotenuse to figure out how light hits the other leg

Edit: the light comes in at the arrow at a right angle. What happens to light at side b and c in the attached pic

 

[th4450]

The angle of incidence i = 0^o since the ray comes at right angle.

 

[NascentOxygen]

What happens to light at side b and c

Consider the ray striking side c and emerging into air. Because air is a less dense medium, that ray as it emerges into air is angled further away from the normal than was the incident ray. Just how much further? https://www.physicsforums.com/images/icons/icon2.gif Apply that formula you provided.