Units of radioactivity: Difference between revisions
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For the quantitative measurement of different aspects of [[radioactivity]], there are a substantial number of '''units of radioactivity'''. The number is relatively high because the aspects include the energy of a radiation source, as well as the effect of [[ionizing radiation]] in air, absorbed in arbitrary materials, and specific effects on biological systems. Doubling the number of units is the reality that they are defined both for the [[International System of Units]] (SI) and in [[U.S. customary units|"traditional" or "customary"]] units. | For the quantitative measurement of different aspects of [[radioactivity]], there are a substantial number of '''units of radioactivity'''. The number is relatively high because the aspects include the energy of a radiation source, as well as the effect of [[ionizing radiation]] in air, absorbed in arbitrary materials, and specific effects on biological systems. Doubling the number of units is the reality that they are defined both for the [[International System of Units]] (SI) and in [[U.S. customary units|"traditional" or "customary"]] units. | ||
{| class="wikitable" | |||
|- | |||
! Property measured | |||
! SI unit | |||
! Other unit | |||
! Notes | |||
|- | |||
| Rate of emission from a source | |||
| | |||
* Becquerel (Bq) | |||
| | |||
* Curie (Ci) | |||
* Counts per minute | |||
| | |||
|- | |||
| Air ionization by radiation | |||
| | |||
* G | |||
rays per hour (Gy/h) | |||
| | |||
* Roentgen (R) | |||
| | |||
* Used for X-rays and gamma radiation | |||
|- | |||
| Absorbed dose | |||
| | |||
* Gray (Gy) | |||
| | |||
* rad | |||
| | |||
* 1 Gray = 100 rad | |||
|- | |||
| Biological equivalent dose | |||
| | |||
* Sievert (Sv) | |||
| | |||
* rem | |||
| | |||
|} | |||
==Radioactive source energy== | ==Radioactive source energy== | ||
1 Bq = 1 event of radiation emission per second. Since this is a very small unit, common measurements are: | |||
*1 kBq = 10<sup>3</sup> Bq | |||
*1 MBq = 10<sup>6</sup> Bq | |||
*1 GBq = 10<sup>9</sup> Bq | |||
The older unit, the Curie (Ci), is equal to 37 GBq. The Curie is a large unit, so common representations are | |||
*1 mCi = 10<sup>-3</sup>Ci | |||
*1 uCi = 10<sup>-6</sup>Ci | |||
*1 nCi = 10<sup>-9</sup>Ci | |||
*1 pCi = 10<sup>-12</sup>Ci | |||
Linking the two sets of units, | |||
<center>1 Bq = 27 pCi</center> | |||
Neither the Bq nor the Ci measure the energy of release from the source, only its rate. The energy is specified in [[electronvolt]]s. | |||
==Ionization of air== | ==Ionization of air== | ||
==Absorption in materials== | ==Absorption in materials== | ||
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==Decay reactions== | ==Decay reactions== | ||
==References== | ==References== | ||
{{reflist}} | |||
Revision as of 00:49, 6 April 2011
For the quantitative measurement of different aspects of radioactivity, there are a substantial number of units of radioactivity. The number is relatively high because the aspects include the energy of a radiation source, as well as the effect of ionizing radiation in air, absorbed in arbitrary materials, and specific effects on biological systems. Doubling the number of units is the reality that they are defined both for the International System of Units (SI) and in "traditional" or "customary" units.
| Property measured | SI unit | Other unit | Notes |
|---|---|---|---|
| Rate of emission from a source |
|
|
|
| Air ionization by radiation |
rays per hour (Gy/h) |
|
|
| Absorbed dose |
|
|
|
| Biological equivalent dose |
|
|
Radioactive source energy
1 Bq = 1 event of radiation emission per second. Since this is a very small unit, common measurements are:
- 1 kBq = 103 Bq
- 1 MBq = 106 Bq
- 1 GBq = 109 Bq
The older unit, the Curie (Ci), is equal to 37 GBq. The Curie is a large unit, so common representations are
- 1 mCi = 10-3Ci
- 1 uCi = 10-6Ci
- 1 nCi = 10-9Ci
- 1 pCi = 10-12Ci
Linking the two sets of units,
Neither the Bq nor the Ci measure the energy of release from the source, only its rate. The energy is specified in electronvolts.