1. The problem statement, all variables and given/known data The data obtained in the experiment is in the graph http://img213.imageshack.us/f/energycalibration.png/ My teacher says that do a linear energy calibration for photopeaks. 3. The attempt at a solution A photopeak seems to be a peak caused by the emission of photons only. My attempt is in the image. I assume that the two last peaks are photopeaks. How would you do the linear energy calibration for the photopeaks of Co60?