A Compton interaction involves a photon interacting with which particle?

In a Compton interaction, a photon interacts primarily with a free electron. This interaction is characterized by the scattering of the photon, resulting in a change in its energy and direction. When a photon collides with a free electron, it transfers a portion of its energy to the electron, causing the electron to be ejected and the photon to be scattered at a different angle with reduced energy. This process highlights the particle-like behavior of photons and the wave-particle duality inherent in quantum mechanics.

In contrast, other particles such as bound electrons, protons, and neutrons do not typically participate in the Compton scattering process in the same way. Bound electrons, for instance, are tightly held within an atom and require different interactions to be ejected. Protons and neutrons, being nucleons found in the nucleus of an atom, do not engage in significant scattering interactions with photons at the energies typically associated with Compton effects. Thus, the interaction is specifically relevant to free electrons, making it the correct choice.