Hi, all I'm seeking advice on how to calculate the energy conversion efficiency, in case of heat from light energy. I think that one of the general formulas 'energy output/energy input' can not be applied in this problem. Assuming that light(or laser) has 10W power output and material 1 exposed to the light source generates heat from 20C' to 30'C for a second, while material 2 generates heat from 20'C to 40'C for a second. In this case, we can say that the energy conversion efficiency is better for material 2, but I want to describe this as a quantitative expression. Please can anyone help me?