Definition

ionizing radiation

Part of the IT standards and organizations glossary:

Ionizing radiation, also (imprecisely) called radioactivity, is electromagnetic ( EM ) radiation whose waves contain energy sufficient to overcome the binding energy of electron s in atom s or molecule s, thus creating ion s. The wavelength is shorter than that of ultraviolet ( UV ).

Ionizing radiation can occur as a barrage of photon s having a nature similar to that of visible light, but with far shorter wavelength and consequently higher frequency . This type of radiation includes X rays and gamma rays. More massive particles also comprise ionizing radiation if they travel at sufficient speed. These include high-speed electrons (beta particles), protons, neutrons, and helium nuclei (alpha particles). Ionizing radiation is dangerous because it damages the internal structures of living cells. This can cause cell death in high doses over a short period of time, and errors in the reproductive process (mutations) in lower doses over longer periods of time.

Examples of non-ionizing EM radiation include radio ( RF ) waves, extremely low frequency ( ELF ) fields, infrared ( IR ), visible light, and UV. These forms of EM energy are generally not dangerous, with some exceptions: high-energy radio microwave s and IR which can cause destructive heating of biological tissue; intense visible light which can cause blindness; and intense UV which can cause blindness and superficial skin burns in high doses over a short period of time, and skin cancer and cataracts of the eye at lower doses over long periods of time. There is debate as to whether long-term exposure to moderate-to-intense radio-frequency (RF) fields and ELF fields is harmful to human beings.

The most common unit of ionizing radiation is the becquerel (Bq), equal to one disintegration or nuclear transformation per second. Reduced to base units in the International System of Units ( SI ), 1 Bq = 1/s or 1 s -1 . An alternative unit is the curie (Ci), equivalent to 3.7 x 10 10 disintegrations per second or 2.2 x 10 12 disintegrations per minute. To convert from curies to becquerels, multiply by 3.7 x 10 10 . To convert from becquerels to curies, multiply by 2.7 x 10 -11 .

This was last updated in September 2005
Posted by: Margaret Rouse

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