please reference the link here This is the gamma spectrum for Co-60 from the wikipedia site:http://en.wikipedia.org/wiki/Gamma_spectroscopy though wikipedia might not be the best of sources, I was just wondering a few things. The two peaks around channel 700 and 800 are referred to as a "photopeak" or "Full Energy Peak." Does this mean that these peaks show the gamma rays that did not interact with atoms or electrons and went right to the detector? Also, the Compton Edge refers to th peak at channel ~570. I read that the peak shows the highest energy that Compton scattering can occur at. With that said, does this mean that from channel 300 to 570 refers to the Compton scattering at different angles and I'm guess at channel 570, the scattering angle is zero? and the peak at ~170 refers to the "backscattering peak" what exactly is that? Also, one last thought. How does the gamma ray's interaction with matter effect this? like if i had a source behind a lead plate vs an aluminum plate, how would that effect the results of the gamma spectrum?