ARRT Practice Exam 2025 – 400 Free Practice Questions to Pass the Exam

The phenomenon that occurs when a low-energy x-ray photon ejects an inner-shell electron is known as the photoelectric effect. In this process, the incoming photon transfers its energy to an electron in an inner shell, such as the K or L shell. If the photon has sufficient energy to overcome the binding energy of the electron, the electron is ejected from the atom, resulting in the ionization of that atom. The energy of the photon must be greater than or equal to the binding energy of the electron for ejection to occur.

This effect is significant in the field of medical imaging and radiation therapy, as it contributes to image formation in diagnostic radiology and affects the dose received by patients. The photoelectric effect is also more likely to occur with higher atomic number materials, such as the tissues being imaged, where the likelihood of interactions is higher due to greater binding energies in denser materials.

The other phenomena mentioned relate to different interactions with x-ray photons. Compton scattering involves the interaction of a photon with a loosely bound outer shell electron, resulting in a change in direction and energy of the photon but not its complete absorption. Pair production refers to a process where a photon with very high energy (greater than 1.022 MeV