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6 Basics of Radiation and Its
Measurement
This chapter briefly tells what radiation is and how it is measured.
This information is provided for users who are not already familiar
with the subject. It is helpful in understanding how the Radalert
100 works and in interpreting your 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, but
generally have a shorter wavelength than X-rays. Gamma rays are
very penetrating; thick lead shielding is generally required to stop
them.