1. The problem statement, all variables and given/known data Hey guys, I am part of a group building a solar oven. It will consist of insulated sides and a glass window on the top. Rather than using reflectors we want to salvage a Fresnel lens from an overhead projector to concentrate sunlight onto the glass window. Part of the assignment is to calculate the steady-state temperature inside the box. 2. Relevant equations How do I calculate the concentration ratio for a Fresnel lens? 3. The attempt at a solution To keep the initial calculation simple I assumed an area of 1 m^2 for the lens (I know this is too big) and 0.25 m^2 for the window. I divided the lens area by the window area to get a concentration ratio of 4. My professor says this is not how you calculate the concentration ratio, and that I should research the correct method.