When a narrow beam of γ-radiation passes through a substance, photons are dropped from the beam as a result of scattering and absorption. In the γ-quantum energy range of 0.03-10 Mee, 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 ...