1. The problem statement, all variables and given/known data Suppose the isosceles prism of the figure(http://imgur.com/EQiQSoO) has apex angle φ = 53.4° and index of refraction n = 1.41. (a) What is the smallest angle of incidence θ for which a ray can enter the left face of the prism and exit the right face? (b) What angle of incidence θ is required for the ray to exit the prism with an identical angle θ for its refraction, as it does in the figure? 2. Relevant equations snells law -- critical angle 3. The attempt at a solution For part A - First I made a triangle then I tried to do a bunch of geometry/trig to find the answer and ended up with nothing. Then I tried to use the critical angle formula where the sine(incident) = 1/n and that did not work either. Been working on this for over an hour now so some help would be amazing!! Haven't even tried part B yet.