|Named after||Henri Becquerel|
|1 Bq in ...||... is equal to ...|
|curie||2.703×10−11 Ci ≅ 27 pCi|
|SI base unit||s−1|
The becquerel (//; symbol: Bq) is the unit of radioactivity in the International System of Units (SI). One becquerel is defined as the activity of a quantity of radioactive material in which one nucleus decays per second. For applications relating to human health this is a small quantity, and SI multiples of the unit are commonly used.
1 Bq = 1 s−1
A special name was introduced for the reciprocal second (s−1) to represent radioactivity to avoid potentially dangerous mistakes with prefixes. For example, 1 µs−1 would mean 106 disintegrations per second: 1·(10−6 s)−1 = 106 s−1, whereas 1 µBq 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. 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. 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 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.
Like any SI unit, Bq can be prefixed; commonly used multiples are kBq (kilobecquerel, 103 Bq), MBq (megabecquerel, 106 Bq, equivalent to 1 rutherford), GBq (gigabecquerel, 109 Bq), TBq (terabecquerel, 1012 Bq), and PBq (petabecquerel, 1015 Bq). Large prefixes are common for practical uses of the unit.
For practical applications, 1 Bq is a small unit. For example, there is roughly 0.017 g of potassium-40 present in a typical human body. This quantity of material decays at a rate of approximately 4,400 decays per second (Bq).
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
- 1 Ci = 3.7×1010 Bq = 37 GBq
- 1 μCi = 37,000 Bq = 37 kBq
- 1 Bq = 2.7×10−11 Ci = 2.7×10−5 μCi
- 1 MBq = 0.027 mCi
The following table shows radiation quantities in SI and non-SI units. WR (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.
|Activity (A)||becquerel||Bq||s−1||1974||SI unit|
|curie||Ci||3.7 × 1010 s−1||1953||3.7×1010 Bq|
|rutherford||Rd||106 s−1||1946||1,000,000 Bq|
|Exposure (X)||coulomb per kilogram||C/kg||C⋅kg−1 of air||1974||SI unit|
|röntgen||R||esu / 0.001293 g of air||1928||2.58 × 10−4 C/kg|
|Absorbed dose (D)||gray||Gy||J⋅kg−1||1974||SI unit|
|erg per gram||erg/g||erg⋅g−1||1950||1.0 × 10−4 Gy|
|rad||rad||100 erg⋅g−1||1953||0.010 Gy|
|Equivalent dose (H)||sievert||Sv||J⋅kg−1 × WR||1977||SI unit|
|röntgen equivalent man||rem||100 erg⋅g−1 × WR||1971||0.010 Sv|
|Effective dose (E)||sievert||Sv||J⋅kg−1 × WR × WT||1977||SI unit|
|röntgen equivalent man||rem||100 erg⋅g−1 × WR × WT||1971||0.010 Sv|
- 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)
- "Radioactivity: Radioactive Activity Doses". radioactivity.eu.com. Retrieved 2020-02-20.
- "Radiation Protection Guidance For Hospital Staff – Stanford Environmental Health & Safety". ehs.stanford.edu. Retrieved 2020-02-20.
- "BIPM - Becquerel". BIPM. Retrieved 2012-10-24.
- Allisy, A. (1995), "From the curie to the becquerel", Metrologia, 32 (6): 467–479, Bibcode:1995Metro..31..467A, doi:10.1088/0026-1394/31/6/006, S2CID 250749337
- "BIPM - Table 3". BIPM. Retrieved 2015-07-19.
(d) The hertz is used only for periodic phenomena, and the becquerel is used only for stochastic processes in activity referred to a radionuclide.
- Harder, D (1976), "[The new radiologic units of measurement gray and becquerel (author's translation from the German original)]", Röntgen-Blätter, 29 (1): 49–52, PMID 1251122.
- Lind, SC (1946), "New units for the measurement of radioactivity", Science, 103 (2687): 761–762, Bibcode:1946Sci...103..761L, doi:10.1126/science.103.2687.761-a, PMID 17836457, S2CID 5343688.
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- "Radioactive Human Body". Harvard Natural Sciences Lecture Demonstrations.
- "Smoke Detector (1970s)". Museum of Radiation and Radioactivity. Retrieved 25 September 2023.
- G.R. Choppin, J.O.Liljenzin, J. Rydberg, "Radiochemistry and Nuclear Chemistry", 3rd edition, Butterworth-Heinemann, 2002. ISBN 978-0-7506-7463-8.
- It was adopted by the BIPM in 1975, see resolution 8 of the 15th CGPM meeting
- Resolution 7 of the 12th CGPM Archived 2021-02-19 at the Wayback Machine (1964)
- Baes, Fred. "hps.org". Health Physics Society. Retrieved 2022-10-03.