(1) Radiobiology. Compton: The fractional number of photons removed from a beam of radiation per unit thickness of material through which it is passing as a result of Compton effect interactions. (2) Linear: The fractional number of photons removed from a beam of radiation per unit thickness of material through which it is passing due to all absorption and scattering processes. (3) Pair Production: That fractional decrease in the intensity of a beam of ionising radiation due to pair production in a medium through which it passes. (4) Photoelectric Effect: That fractional decrease in the intensity of a beam of ionising radiation due to photoelectric effect in a medium through which it passes. Attenuation Coefficient is a quantity that characterizes how easily a material or medium can be penetrated by a beam of light, sound, particles, or other energy or matter. A large attenuation coefficient means that the beam is quickly "attenuated" (weakened) as it passes through the medium, and a small attenuation coefficient means that the medium is relatively transparent to the beam. Attenuation coefficient is measured using units of reciprocal length. The attenuation coefficient is also called linear attenuation coefficient, narrow beam attenuation coefficient, orabsorption coefficient. Although all four terms are often used interchangeably, they can occasionally have a subtle distinction, as explained below. An OSH glossary used in safety and health at work which is, adopted by ILO