The becquerel, symbol , is the SI unit of radioactive activity, with . An radioactive activity of one becquerel means one expected nuclear transformation per second under the stated conditions, not a guarantee of one event in every individual second.
Measured count rate need not equal radioactive activity. A particle detector registers only some decays because of geometry and detection efficiency, and one transformation can emit several particles or none detectable by that instrument. Activity also differs from deposited energy or absorbed dose: those depend on the emitted particles, their energies and where their interactions occur.
Articles by others on the same topic
Becquerel (symbol: Bq) is the SI unit of radioactivity. It measures the activity of a quantity of radioactive material, specifically the number of disintegrations (or decay events) that occur in a sample per second. One becquerel is defined as one disintegration per second. The unit is named after Henri Becquerel, a French physicist who discovered radioactivity in 1896.