Undergraduate Relativity Experiment

The primary electrons in a γ-ray detector crystal are typically rather relativistic having kinetic energies of the order of their own rest mass. A technique is described which enables the student to observe the relativistic behavior of these electrons and compare his results with the classical and relativistic predictions. It is shown that it is possible to unambiguously determine the electron's momentum by knowing the Compton edge and photopeak energies of a γ-ray energy spectrum.