Browse Definitions:

ionizing radiation

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

Start the conversation

Send me notifications when other members comment.

By submitting you agree to receive email from TechTarget and its partners. If you reside outside of the United States, you consent to having your personal data transferred to and processed in the United States. Privacy

Please create a username to comment.


File Extensions and File Formats


  • risk map (risk heat map)

    A risk map, also known as a risk heat map, is a data visualization tool for communicating specific risks an organization faces. A...

  • internal audit (IA)

    An internal audit (IA) is an organizational initiative to monitor and analyze its own business operations in order to determine ...

  • pure risk (absolute risk)

    Pure risk, also called absolute risk, is a category of threat that is beyond human control and has only one possible outcome if ...


  • federated identity management (FIM)

    Federated identity management (FIM) is an arrangement that can be made among multiple enterprises to let subscribers use the same...

  • cross-site scripting (XSS)

    Cross-site scripting (XSS) is a type of injection security attack in which an attacker injects data, such as a malicious script, ...

  • firewall

    In computing, a firewall is software or firmware that enforces a set of rules about what data packets will be allowed to enter or...




  • bad block

    A bad block is an area of storage media that is no longer reliable for storing and retrieving data because it has been physically...

  • all-flash array (AFA)

    An all-flash array (AFA), also known as a solid-state storage disk system, is an external storage array that uses only flash ...

  • volume manager

    A volume manager is software within an operating system (OS) that controls capacity allocation for storage arrays.


  • hybrid hard disk drive (HDD)

    A hybrid hard disk drive is an electromechanical spinning hard disk that contains some amount of NAND Flash memory.