1. The energy of a photon, after being Compton scattered from an electron at rest through an angle of 60° is half its initial energy. Calculate its initial energy. 2. Consider the region close to a nuclear reactor that produces large fluxes of prompt gamma rays with energies of about 7 MeV. Use the graph below, showing the mass attenuation coefficient of gamma rays in different stopping media as a function of energy, to determine the approximate thickness of lead shielding which would be required to reduce the gamma flux by a factor of 1010. The density of lead is 11.3 g cm³. Attenuation coefficient (cm²g) 10 Pb 0.5 0.1 0.05 Pb Cu AL 0.01 0.01 0.05 0.1 0.5 1 5 10 50 100 Energy (MeV)

1. The energy of a photon, after being Compton scattered from an electron at rest through an angle of 60° is half its initial energy. Calculate its initial energy. 2. Consider the region close to a nuclear reactor that produces large fluxes of prompt gamma rays with energies of about 7 MeV. Use the graph below, showing the mass attenuation coefficient of gamma rays in different stopping media as a function of energy, to determine the approximate thickness of lead shielding which would be required to reduce the gamma flux by a factor of 1010. The density of lead is 11.3 g cm³. Attenuation coefficient (cm²g) 10 Pb 0.5 0.1 0.05 Pb Cu AL 0.01 0.01 0.05 0.1 0.5 1 5 10 50 100 Energy (MeV)