Hello, I need some information about spherical mirrors that I can't find in internet or this forum. How to calculate the amount of light that is focused in the mirror's focus point depending on the mirror's area and the amount of light emited by the source? If that light is reflected by another plain mirror to another point, is there any loss of light? I mean loss of efficiency. The purpose of my questions is if I want certain amount of light, how can I calculate the spherical mirror's area and to take into account any losses? Thanks!