Counting efficiency
![Graphic showing relationships between radioactivity and detected ionizing radiation](/Images/godic/202501/06/Radioactivity_and_radiation2412.png")
![Hand-held large area alpha scintillation probe under calibration using a plate source in close proximity to the detector.](/Images/godic/202501/06/US_Navy_070208-N-9132D-002_Electronics_Technician_2nd_Class_Shea_Thompson_tests_an_Alpha_Particle_Dection_Probe2412.jpg")
![Schematic of a Geiger counter using an](/Images/godic/202501/06/Geiger-Muller-counter-en2412.png")
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.