Simple Law of Refraction Problem

[opticaltempest]

Homework Statement

I am studying the Law of Refraction. I am at a point in my textbook called a "checkpoint". These are supposed to be simple questions to test understanding. I'm apparently not understanding thus far because I cannot figure out this problem.

http://img262.imageshack.us/img262/7029/refractionqn3.jpg

Homework Equations

Snell's Law?

The Attempt at a Solution

I'm sure the angles of line segments b and c (relative to a?) will be the determining factor. Since the problem says "original materials a" does that mean we measure all angles relative to line segment a? How do I proceed more mathematically on this problem - perhaps using Snell's law?

 

[Doc Al]

Definitely use Snell's law. Measure angles with respect to the normal, as usual with Snell's law.