1. The problem statement, all variables and given/known data (Refraction) A parallel beam of width W is incident on a interface. The index of refractions are n1 on the incident side and n2 on the transmitted side. (a) Find an equation that gives the width of the transmitted beam. (Assume there is an exit beam. IE we are not above the angle of total internal reﬂection.) 2. Relevant equations n1 sin theta1 = n2 sin theta2 3. The attempt at a solution If I draw a diagram, it seems that the refracted width is the same as the incident width. Anyone care to explain?