1. The problem statement, all variables and given/known data This is the given question. The blue rays represent the solution. http://img16.imageshack.us/img16/7237/lenstq.jpg [Broken] 2. Relevant equations None. 3. The attempt at a solution The blue rays are essentially my solutions, but only up to the point where the rays are reflected off the mirror. The rays after hitting the lens after that are from my teacher. Once they hit the lens, I know the 2 rays need to converge at a point along the focal plane, since the rays are parallel. What I want to know is why is the image the same size as the object?