Attenuation Mechanisms Photoelectric Effect) (b)Photoelectric effect The photon,E slightly greater than E b gives up all of its energy to an inner shell electron,thereby ejecting it from the atom.The excited atom retains to the ground state with the emission of characteristic photons.Most of these are of relatively low energy and are absorbed by the material. Attenuation Mechanisms ( Photoelectric Effect) ( b) Photoelectric effect The photon, E slightly greater than E b gives up all of its energy to an inner shell electron, thereby ejecting it from the atom. The excited atom retains to the ground state with the emission of characteristic photons. Most of these are of relatively low energy and are absorbed by the material