readings.
Ionizing Radiation
Ionizing radiation is radiation that changes the structure of individual atoms by
ionizing them. The ions produced in turn ionize more atoms. Substances that
produce ionizing radiation are called radioactive.
Radioactivity is a natural phenomenon. Nuclear reactions take place
continuously on the sun and all other stars. The emitted radiation travels
through space, and a small fraction reaches the Earth. Natural sources of
ionizing radiation also exist in the ground. The most common of these are
uranium and its decay products.
Ionizing radiation is categorized into four types:
X-rays are usually manmade radiation produced by bombarding a metallic target
with electrons at a high speed in a vacuum. X-rays are electromagnetic
radiation of the same nature as light waves and radio waves, but at extremely
short wavelength, less than 0.1 billionth of a centimeter. They are also called
photons. The energy of X-rays is millions of times greater than that of light and
radio waves. Because of this high energy level, X rays penetrate a variety of
materials, including body tissue.
Gamma rays occur in nature and are almost identical to X rays. Gamma rays
generally have a shorter wavelength than X-rays. Gamma rays are very
penetrating; thick lead shielding is generally required to stop them.
Beta radiation. A beta particle consists of an electron emitted from an atom. It
has more mass and less energy than a gamma ray, so it doesn't penetrate
matter as deeply as gamma and X-rays.
Alpha radiation. An alpha particle consists of two protons and two neutrons, the
same as the nucleus of a helium atom. It generally can travel no more than 1 to
3 inches in air before stopping, and can be stopped by a piece of paper.
When an atom emits an alpha or beta particle or a gamma ray, it becomes a
different type of atom. Radioactive substances may go through several stages
of decay before they change into a stable, or non-radioactive, form.
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