1. The problem statement, all variables and given/known data I am given the following figure: These are converging rays that appear to be going to a point F convert to a plane wave upon hitting the boundary between n2 and n1, and I am asked to find the equation for the boundary between n1 and n2 that perfectly accomplishes this conversion to a plane wave. Assume the distance between the vertex of the boundary and the point F is a known quantity. 2. Relevant equations 3. The attempt at a solution I believe the answer is 1/f = 1/n1 + 1/n2 But I am not sure how to get to this answer. Could someone please explain the steps and help me understand the problem? Thanks.