count-rate – the number of radioactive decays detected per unit of time (pulses per second)

To remember the meaning of count-rate, use the following mnemonic:

Count Dracula measured the rate (count-rate) of radiation per decade (radioactive decay over time).

Count-rate is a measure of the number of radioactive decay events or radiation particles detected by a radiation detector, such as a Geiger-Muller tube, in a given period of time, typically expressed in counts per second or counts per minute. This measurement provides information about the activity or intensity of a radioactive source, with a higher count-rate indicating more radiation being emitted and detected.

Count-rate measurements are used in various applications including monitoring the decay of radioactive sources over time to determine half-life, checking for radiation contamination and ensuring safety in workplaces that handle radioactive materials. As a radioactive source decays over time, its count-rate decreases following an exponential decay pattern as can be seen in the following graph: