Becquerel 155835 221054257 2008-06-22T21:21:28Z VolkovBot 3035831 robot Adding: [[be:Бекерэль, адзінка вымярэння]] {{citations}} {{otheruses}} The '''becquerel''' (symbol '''Bq''') is the [[SI derived unit]] of [[Radioactive decay|radioactivity]], defined as the [[activity (radioactivity)|activity]] of a quantity of radioactive material in which one [[atomic nucleus|nucleus]] decays per [[second]]. It is therefore equivalent to [[second|s]]<sup>-1</sup>. The becquerel is named for [[Henri Becquerel]], who shared a [[Nobel Prize]] with [[Pierre Curie|Pierre]] and [[Maria Sklodowska-Curie|Marie Curie]] for their work in discovering radioactivity. In a fixed mass of radioactive material, the number of becquerels changes with time. Therefore, a sample radioactive decay rate is always stated with a timestamp for short-lived isotopes, sometimes after adjustment to some specific date of interest (in the past or in the future). For example, one might quote a ten-day adjusted figure, that is, the amount of radioactivity that will still be present ten days in the future. This can de-emphasize short-lived isotopes. [[International System of Units|SI]] uses the becquerel rather than the second for the unit of activity measure to avoid dangerous mistakes: a measurement in becquerels is proportional to activity, and thus a more dangerous source of radiation gives a higher reading. A measurement in seconds is inversely proportional. As any SI unit, Bq can be [[SI prefix|prefixed]]; commonly used multiples are kBq (kilobecquerel, 10<sup>3</sub> Bq), MBq (megabecquerel, 10<sup>6</sup> Bq), and GBq (gigabecquerel, 10<sup>9</sup> Bq). When measuring radioactivity of a sample with a detector, a unit of "counts per second" (cps) or "[[counts per minute]]" (cpm) are often used. These units can be converted to the absolute activity of the sample in Bq if one applies a number of significant conversions, e.g., for the radiation background, for the detector efficiency, for the counting geometry, for self-absorption of the radiation in the sample. The becquerel can be used for the frequency of aperiodic events; for periodic events, the [[hertz]], which is also defined as s<sup>–1</sup>, is used as unit. == Relationship to the curie == The [[curie]] (Ci) is an older, non-SI unit, of radioactivity. It is equivalent to 3.70 × 10<sup>10</sup> disintegrations per second, which is approximately the amount of activity produced by 1 g of radium-226. Thus the curie is defined as 3.7&times;10<sup>10</sup> becquerels or 37 GBq. ==Definition== 1 Bq = 1 s<sup>–1</sup> {{SI unit lowercase|Henri Becquerel|becquerel|Bq}} ==External links== * [http://www1.bipm.org/en/si/derived_units/2-2-2.html Derived units] on the [[BIPM]] web site <!--Categories--> [[Category:SI derived units]] [[Category:Units of radioactivity]] [[Category:Units of frequency]] <!--Interwiki--> [[be:Бекерэль, адзінка вымярэння]] [[be-x-old:Бэкэрэль (адзінка вымярэньня)]] [[bg:Бекерел]] [[ca:Becquerel (unitat)]] [[cs:Becquerel]] [[da:Becquerel]] [[de:Becquerel (Einheit)]] [[et:Bekrell]] [[es:Becquerel]] [[eo:Bekerelo]] [[fr:Becquerel]] [[ko:베크렐]] [[id:Becquerel]] [[is:Bekerel]] [[it:Becquerel]] [[he:בקרל]] [[lt:Bekerelis]] [[ms:Becquerel]] [[nl:Becquerel]] [[ja:ベクレル]] [[no:Becquerel]] [[nn:Becquerel]] [[nds:Becquerel (Eenheit)]] [[pl:Bekerel]] [[pt:Becquerel]] [[ro:Becquerel]] [[ru:Беккерель (единица измерения)]] [[simple:Becquerel]] [[sk:Becquerel (jednotka)]] [[sl:Bekerel]] [[sr:Бекерел]] [[sh:Bekerel]] [[fi:Becquerel]] [[sv:Becquerel]] [[vi:Becơren]] [[tr:Bekerel]] [[uk:Бекерель]] [[zh:放射性活度]]