Counting efficiency
In the measurement of ionising radiation the counting efficiency is the ratio between the number of particles or photons counted with a radiation counter and the number of particles or photons of the same type and energy emitted by the radiation source. == Factors == Several factors affect the counting efficiency: The distance from the source of radiation The absorption or scattering of particles by the medium (such as air) between the source and the surface of the detector The detector efficiency in counting all radiation photons and particles that reach the surface of the detector The accompanying diagram shows this graphically.