1. The problem statement, all variables and given/known data (Preface: I am not a physicist) The pulse height spectrum of a radioactive source known to emit high energy photons was measured using a small detector. Three distinct peaks were observed at heights of 7.38, 6.49 and 5.60 V, along with a continuous portion of the spectrum. i) Describe the processes involved in the origin of these peaks. ii) What is the initial gamma-ray energy? 2. Relevant equations 3. The attempt at a solution The detector is specified as small, so singular photon reactions are presumed. From my very limited knowledge, i assumed the largest peak to be the photopeak/ full energy peak, and perhaps the other peaks were related to double escape from pair production or a compton peak from backscatter. As mentioned above, I am not a physicist, so be gentle!