1. The problem statement, all variables and given/known data Beam of electrons (charged particles!) is directed to copper absorber with known energy (E= 10MeV) and intensity (10^8(s*cm^2)^-1) . I need to find the thickness of absorber so that all electrons would be absorbed. Also under what conditions does it happen and what is absorbed dose then? 2. Relevant equations D=(1.602*10^-10)* (fluence*E/mass thickness) (Gy) 3. The attempt at a solution so to get absorber thickness should I mass stopping power multiply by copper density and then divide it from the beam energy? is it thick foil condition?