What Is the Smallest Angle of Incidence for Light to Enter and Exit a Prism?

[NW8800]

Hey,

I have a problem.,. I am trying to figure out smallest angle of incidence θ for which a ray can enter the left face of the prism (seen in the pic below) and exit the right face.

The infomation I have:

The isosceles prism has apex angle φ = 56.1° and index of refraction n = 1.42

Diagram:
http://img520.imageshack.us/img520/5857/fig3355xp0.gif

Can someone giver me an answer on this?

Thanks,

NW

 

[Meir Achuz]

Work backwards from the critical angle at exit.