1. The problem statement, all variables and given/known data I have this task: A collimated monochromatic beam of photons with intensity 10^20/s and energy 10 MeV is directed to a iron absorber with thickness 3 cm. What kind of interactions are expected? Suppose, each interaction removes one particle from the beam. I need to know, what amount of energy does each type of interaction remove from the beam? 2. Relevant equations N=N0(1-e^(-Δx μ)) equations of cross sections 3. The attempt at a solution I think, that here may be expected photoelectric, compton, pair production interactions. To get amount of energy removed by each interaction I need to know number of interactions and then multiply it by the energy, but I also need to know number of photons to get the number of interactions, or I am very wrong?