How do gamma rays commonly used for testing undergo attenuation?

Gamma rays commonly undergo attenuation through two primary processes: photoelectric absorption and Compton scattering, which are essential mechanisms that affect the intensity of gamma radiation as it travels through matter.

In photoelectric absorption, a gamma photon interacts with an electron in an atom, transferring all of its energy to the electron, which is then ejected from the atom. This process occurs more readily in materials with high atomic numbers and at lower gamma-ray energies. The photon essentially disappears, contributing to the attenuation of the radiation.

Compton scattering, on the other hand, occurs when a gamma photon collides with an outer electron, imparting only part of its energy to the electron while the photon is deflected with reduced energy. This interaction is significant at intermediate photon energies and results in a redistribution of energy, contributing to the overall attenuation of the beam.

Together, these processes define how gamma rays lose intensity as they traverse various materials, forming a critical understanding in radiographic testing and the evaluation of material properties. The other options mention processes that do not significantly contribute to the attenuation of gamma rays in the context of radiographic testing, making them less relevant to the question.