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{{Short description|SI derived unit of radioactivity}}{{Redirect-multi|2|Bq|MBq|other uses|BQ (disambiguation){{!}}BQ|and|MBQ (disambiguation){{!}}MBQ|and|Becquerel (disambiguation)}}

factoids

Curie (unit)>curie2.703u=Ci}} ≅ {{valu=pCi}}| units3 = SI base unitsecond>s−1}}The becquerel ({{IPAc-en|ˌ|b|ɛ|k|ə|ˈ|r|ɛ|l}}; symbol: Bq) is the unit of radioactivity in the International System of Units (SI). One becquerel is defined as an activity of one decay per second. For applications relating to human health this is a small quantity,WEB, Radioactivity: Radioactive Activity Doses,weblink dead,weblink 2020-02-20, 2020-02-20, radioactivity.eu.com, and SI multiples of the unit are commonly used.WEB, Radiation Protection Guidance For Hospital Staff – Stanford Environmental Health & Safety,weblink ehs.stanford.edu, 2020-02-20, The becquerel is named after Henri Becquerel, who shared a Nobel Prize in Physics with Pierre and Marie Curie in 1903 for their work in discovering radioactivity.WEB,weblink BIPM - Becquerel, BIPM, 2012-10-24,

Definition

1 Bq = 1 s−1A special name was introduced for the reciprocal second (s{{sup|−1}}) to represent radioactivity to avoid potentially dangerous mistakes with prefixes. For example, 1 Î¼s{{sup|−1}} would mean 10{{sup|6}} disintegrations per second: (10{{sup|−6}} s){{sup|−1}} = 10{{sup|6}} s{{sup|−1}},{{Citation|last=Allisy|first= A.|title=From the curie to the becquerel|journal=Metrologia|volume=32|issue=6|year=1995|pages=467–479|doi=10.1088/0026-1394/31/6/006|bibcode = 1995Metro..31..467A|s2cid= 250749337}} whereas 1 Î¼Bq would mean 1 disintegration per 1 million seconds. Other names considered were hertz (Hz), a special name already in use for the reciprocal second, and fourier (Fr; after Joseph Fourier). The hertz is now only used for periodic phenomena.WEB,weblink BIPM - Table 3, BIPM, (d) The hertz is used only for periodic phenomena, and the becquerel is used only for stochastic processes in activity referred to a radionuclide., 2015-07-19, While 1 Hz is one cycle per second, 1 Bq is one event per second on average for aperiodic radioactive decays.The gray (Gy) and the becquerel (Bq) were introduced in 1975.{{Citation|last=Harder|first=D|year=1976|title=[The new radiologic units of measurement gray and becquerel (author's translation from the German original)]|journal=Röntgen-Blätter|volume=29|issue=1 |pages=49–52 |pmid=1251122 |postscript=.}} Between 1953 and 1975, absorbed dose was often measured in rads. Decay activity was measured in curies before 1946 and often in rutherfords between 1946{{Citation|last=Lind|first=SC|year=1946|title=New units for the measurement of radioactivity|journal=Science|volume=103|issue=2687|pages=761–762|pmid=17836457|doi=10.1126/science.103.2687.761-a|postscript=.|bibcode=1946Sci...103..761L |s2cid=5343688 }} and 1975.

Unit capitalization and prefixes

As with every International System of Units (SI) unit named after a person, the first letter of its symbol is uppercase (Bq). However, when an SI unit is spelled out in English, it should always begin with a lowercase letter (becquerel)—except in a situation where any word in that position would be capitalized, such as at the beginning of a sentence or in material using title case.WEB, SI Brochure: The International System of Units (SI),weblink 8, 2014, SI Brochure, BIPM, Like any SI unit, Bq can be prefixed; commonly used multiples are kBq (kilobecquerel, 10{{sup|3}} Bq), MBq (megabecquerel, 10{{sup|6}} Bq, equivalent to 1 rutherford), GBq (gigabecquerel, 10{{sup|9}} Bq), TBq (terabecquerel, 10{{sup|12}} Bq), and PBq (petabecquerel, 1015 Bq). Large prefixes are common for practical uses of the unit.

Examples

For practical applications, 1 Bq is a small unit. For example, there is roughly 0.017 g of potassium-40 in a typical human body, producing about 4,400 decays per second (Bq).WEB, Radioactive Human Body,weblink Harvard Natural Sciences Lecture Demonstrations, The activity of radioactive americium in a home smoke detector is about 37 kBq (1 Î¼Ci).WEB, Smoke Detector (1970s),weblink Museum of Radiation and Radioactivity, 25 September 2023, en, The global inventory of carbon-14 is estimated to be {{val|8.5|e=18|u=Bq}} (8.5 EBq, 8.5 exabecquerel).G.R. Choppin, J.O.Liljenzin, J. Rydberg, "Radiochemistry and Nuclear Chemistry", 3rd edition, Butterworth-Heinemann, 2002. {{ISBN|978-0-7506-7463-8}}.These examples are useful for comparing the amount of activity of these radioactive materials, but should not be confused with the amount of exposure to ionizing radiation that these materials represent. The level of exposure and thus the absorbed dose received are what should be considered when assessing the effects of ionizing radiation on humans.

Relation to the curie

The becquerel succeeded the curie (Ci),It was adopted by the BIPM in 1975, see resolution 8 of the 15th CGPM meeting an older, non-SI unit of radioactivity based on the activity of 1 gram of radium-226. The curie is defined as {{val|3.7|e=10|u=s-1}}, or 37 GBq.Resolution 7 of the 12th CGPM {{Webarchive|url=https://web.archive.org/web/20210219084448weblink |date=2021-02-19 }} (1964)Conversion factors:

• 1 Ci = {{val|3.7|e=10|u=Bq}} = 37 GBq
• 1 μCi = 37,000 Bq = 37 kBq
• 1 Bq = {{val|2.7|e=-11|u=Ci}} = {{val|2.7|e=-5|u=μCi}}
• 1 MBq = 0.027 mCi

Relation to other radiation-related quantities

(File:Radioactivity and radiation.png|thumb|upright=2|Graphic showing relationships between radioactivity and detected ionizing radiation)The following table shows radiation quantities in SI and non-SI units. W{{sub|R}} (formerly 'Q' factor) is a factor that scales the biological effect for different types of radiation, relative to x-rays (e.g. 1 for beta radiation, 20 for alpha radiation, and a complicated function of energy for neutrons). In general, conversion between rates of emission, the density of radiation, the fraction absorbed, and the biological effects, requires knowledge of the geometry between source and target, the energy and the type of the radiation emitted, among other factors.WEB, Baes, Fred, hps.org,weblink 2022-10-03, Health Physics Society, {{nonspecific|date=January 2024}}{{Radiation related quantities}}

See also

• Background radiation
• Banana equivalent dose
• Counts per minute
• Ionizing radiation
• Orders of magnitude (radiation)
• Radiation poisoning
• Relative biological effectiveness
• Rem (unit)
• Rutherford (unit)
• Sievert (biological dose equivalent of radiation)

References

{{Reflist|2}}

External links

{{wiktionary}}

• weblink" title="web.archive.org/web/20050316054529weblink">Derived units on the International Bureau of Weights and Measures (BIPM) web site

{{Radiation protection}}{{SI units}}