When a narrow beam of γ‑radiation passes through a substance, photons are removed from the beam as a result of scattering and absorption. In the γ‑quantum energy range of 0.03‑10 MeV, which is of interest for radiometry and nuclear geophysics, the main processes leading to attenuation of the γ‑quantum flux are: photoelectric absorption, coherent and Compton scattering, formation of electron‑positron pairs ...