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Sciencetime© 2009
reproduction by permission of
author
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Ionizing & Non-Ionizing
Radiation
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| Radiation having a wide range of energies form the
electromagnetic spectrum, which is illustrated below. The spectrum has
two major divisions: non-ionizing and ionizing radiation.
Radiation that has enough energy to move atoms in a molecule around
or cause them to vibrate, but not enough to remove electrons, is
referred to as "non-ionizing radiation." Examples of this kind of
radiation are sound waves, visible light, and microwaves.
Radiation that falls within the ionizing radiation" range has enough
energy to remove tightly bound electrons from atoms, thus creating ions.
This is the type of radiation that people usually think of as
'radiation.' We take advantage of its properties to generate electric
power, to kill cancer cells, and in many manufacturing processes.
The energy of the radiation shown on the spectrum below increases
from left to right as the frequency rises.
Non-ionizing Radiation
We take advantage of the properties of non-ionizing radiation for
common tasks:
 | microwave radiation-- telecommunications and heating food
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| infrared radiation --infrared lamps to keep food warm in
restaurants
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| radio waves-- broadcasting
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Non-ionizing radiation ranges from extremely low frequency
radiation, shown on the far left through the audible, microwave, and
visible portions of the spectrum into the ultraviolet range.
Extremely low-frequency radiation has very long wave lengths (on
the order of a million meters or more) and frequencies in the range of
100 Hertz or cycles per second or less. Radio frequencies have wave
lengths of between 1 and 100 meters and frequencies in the range of 1
million to 100 million Hertz. Microwaves that we use to heat food
have wavelengths that are about 1 hundredth of a meter long and have
frequencies of about 2.5 billion Hertz.
Ionizing Radiation
Higher frequency ultraviolet radiation begins to have enough energy
to break chemical bonds. X-ray and gamma ray radiation, which are at
the upper end of magnetic radiation have very high frequency --in the
range of 100 billion billion Hertz--and very short wavelengths --1
million millionth of a meter. Radiation in this range has extremely
high energy. It has enough energy to strip off electrons or, in the
case of very high-energy radiation, break up the nucleus of atoms.
Ionization is the process in which a charged portion of a molecule
(usually an electron) is given enough energy to break away from the
atom. This process results in the formation of two charged particles
or ions: the molecule with a net positive charge, and the free
electron with a negative charge.
Each ionization releases approximately 33 electron volts (eV) of
energy. Material surrounding the atom absorbs the energy. Compared to
other types of radiation that may be absorbed, ionizing radiation
deposits a large amount of energy into a small area. In fact, the 33
eV from one ionization is more than enough energy to disrupt the
chemical bond between two carbon atoms. All ionizing radiation is
capable, directly or indirectly, of removing electrons from most
molecules.
There are three main kinds of ionizing radiation:
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