What does becquerel mean?
The becquerel is the International System of Units (SI) measure of radioactivity, defined as the activity of a quantity of radioactive material in which one nucleus decays per second. It carries the symbol Bq and replaced the older, far larger curie in official use. The unit honours Henri Becquerel, the French physicist who discovered natural radioactivity in 1896, work for which he shared the 1903 Nobel Prize with Pierre and Marie Curie. In practice, the becquerel appears wherever radiation is monitored: food safety agencies quote contamination limits in becquerels per kilogram or per litre, environmental bodies track airborne activity after nuclear incidents, and hospitals use it to calibrate radiopharmaceutical doses. Because individual atomic decays are frequent even in tiny samples, everyday figures are usually large multiples such as kilobecquerels, making the unit a familiar shorthand in reporting on nuclear safety and health risks.
nounThe SI derived unit of radioactivity, equal to one nuclear disintegration (decay) per second. It is named after the French physicist Henri Becquerel, the discoverer of radioactivity.
- The SI derived unit of radioactive activity, equal to one nuclear decay per second (symbol Bq).
"Regulators found that the water sample contained 300 becquerels of caesium-137 per litre."
"After the accident, monitoring stations recorded elevated becquerel counts in the surrounding air."
"Milk samples were withdrawn from sale when they exceeded the permitted limit of 500 becquerels per kilogram."
Regular plural; used when stating quantities, e.g. measurements of radioactive activity.
"The soil contained several thousand becquerels of radioactive material per square metre."
One becquerel means exactly one atom decaying every second — which is why ordinary bananas register around 15 of them.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of becquerel
The word is an eponym formed directly from the surname of Henri Becquerel (1852–1908), the French physicist who discovered spontaneous radioactivity in 1896 while investigating phosphorescence in uranium salts. The unit was adopted internationally in 1975 by the General Conference on Weights and Measures as part of the SI system, replacing the earlier curie. The name itself is a common French surname of long standing in France, and the term entered English unchanged from French alongside other eponymous scientific units such as the joule, watt, and hertz.
How becquerel is actually used
A technical term used mainly in scientific, medical, regulatory, and journalistic contexts involving radiation measurement. It takes the standard plural 'becquerels' when used countably; in scientific writing it often appears with its symbol 'Bq'. Because a single becquerel represents a very small amount of activity, real-world measurements are frequently reported in kilobecquerels or megabecquerels.
Easily confused with becquerel
The curie is an older, non-SI unit of radioactivity equal to 37 billion becquerels; the becquerel is the much smaller modern SI unit.