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[RadCCORE Wiki Home Page :: Definitions :: This page]
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ionizing radiation |
Ionizing radiation is either
particle radiation or
electromagnetic radiation in which an individual particle/photon carries enough energy to ionize an atom or molecule by completely removing an electron from its orbit. If the individual particles do not carry this amount of energy, it is essentially impossible for even a large flood of particles to cause ionization. These ionizations, if enough occur, can be very destructive to living tissue, and can cause DNA damage and mutations.
Examples of particle radiation that are ionizing may be energetic
electrons,
neutrons, atomic ions or
photons. Electromagnetic radiation can cause ionization if the energy per photon, or
frequency, is high enough, and thus the
wavelength is short enough. The amount of energy required varies between molecules being ionized. Far
ultraviolet,
x-rays, and
gamma rays are all always ionizing radiation; near ultraviolet and visible light are ionizing to some molecules; microwaves and radio waves are non-ionizing radiation.
Ionizing radiation is produced by
radioactive decay,
nuclear fission and
nuclear fusion, by extremely hot objects (the hot sun, e.g., produces ultraviolet), and by
particle accelerators that may produce, e.g., fast electrons or protons or
bremsstrahlung or
synchrotron radiation.
In order for radiation to be ionizing, the particles must both have a high enough energy and interact with electrons. Photons interact strongly with charged particles, so photons of sufficiently high energy are ionizing. The energy at which this begins to happen is in the
ultraviolet region; sunburn is one of the effects of this ionization. Charged particles such as
electrons,
positrons, and
Alpha Particles also interact strongly with electrons.
neutrons, on the other hand, do not interact strongly with electrons, and so they cannot directly ionize atoms. They can interact with atomic nuclei, depending on the nucleus and their velocity, these reactions happen with
fast neutrons and
slow neutrons, depending on the situation. Neutron radiation often produces
radioactive nuclei, which produce ionizing radiation when they decay.
The negatively charged electrons and positively charged
ions created by ionizing radiation may cause damage in living tissue. If the dose is sufficient, the effect may be seen almost immediately, in the form of
radiation poisoning. Lower doses may cause
cancer or other long-term problems. The effect of the very low doses encountered in normal circumstances (from both natural and artificial sources, like cosmic rays, medical X-rays and nuclear power plants) is a subject of current debate. A 2005 report released by the National Research Council (the BEIR VII report, summarized in [
http://www.nap.edu/execsumm_pdf/11340.pdf]) indicated that the overall cancer risk associated with background sources of radiation was relatively low.
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Last modified: 29.08.06 by jross
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