Which of the following is one of the important interactions involving X-rays and gamma rays?

Photoelectric absorption is a significant interaction involving X-rays and gamma rays, whereby photons are completely absorbed by an atom. This process leads to the ejection of an inner shell electron from the atom, which results in ionization. The energy of the incident photon must be greater than the binding energy of the electron for this interaction to occur.

When photoelectric absorption takes place, it has a variety of consequences, such as the emission of characteristic X-rays as the atom stabilizes, contributing to the overall image and data quality in radiographic techniques. This is particularly important in medical imaging and radiation therapy, as it can affect dose distribution in tissues based on their composition.

On the other hand, while elastic scattering, Rayleigh scattering, and thermal radiation are related to interactions involving electromagnetic radiation, they do not represent the direct absorption process that is characteristic of photoelectric absorption. Elastic scattering involves the conservation of energy and momentum without any energy absorption, Rayleigh scattering refers to the elastic scattering of light or other electromagnetic radiation, particularly at lower energies, and thermal radiation is emitted from objects based on their temperature, which is not a direct interaction with X-rays or gamma rays in the same context.