1. A photon having 40 keV scatters from a free electron at rest. What is the maximum energy that the electron can obtain?
2. If a 7.0-keV photon scatters from a free proton at rest, what is the change in the photon's wavelength if the photon recoils at 90°?
3. Is it possible to have a scattering similar to Compton scattering from a proton in H2 gas? What would be the Compton wavelength for a proton? What energy photon would have this wavelength?