What Is Radiation?

Basically speaking, radiation is a form of energy transmitted through the air as an electromagnetic wave. As well as being naturally present in the environment, radiation also comes from man-made sources such as medical and industrial activities.

Fig. 1: Types of radiation in daily life. The electromagnetic spectrum covers a wide range of wavelengths.

Fig. 1: Types of radiation in daily life. The electromagnetic spectrum covers a wide range of wavelengths.

The most familiar form of radiation is visible sunlight, consisting of radiation in a range of wavelengths from the longer infra-red to shorter ultraviolet rays. In addition to this radiation from the sun, there are other kinds of radiation that we all receive in low doses. As well as coming from space, these come from the earth, the air we breathe and man-made sources such as those used in medicine (Figure 1) 1.

We divide all these forms of radiation into two categories: ionizing and non-ionizing radiation. Ions are forms of atoms and molecules that have either a positive or negative electrical charge. Radiation that causes them to become ions is known as ionizing radiation. Non-ionizing radiation, on the other hand, doesn’t have sufficient energy to cause this change of state.

We all receive some exposure to natural background radiation as well as occasional man-made radiation such as medical or dental x-rays.

  • Non-ionizing Radiation

    Non-ionizing radiation has less energy than ionizing radiation and includes forms such as microwaves or radio and television waves. Its effect is generally limited to generating light or heat.

  • Fig. 2: Ionization is the process where an electron is ejected from an atom, which then becomes electrically charged.

    Ionizing Radiation

    Ionizing radiation consists of electromagnetic waves with sufficient energy to cause electrons to become detached from atoms and molecules in the matter they pass through, changing their structure – a process known as ionization.

1. Modified according to: http://www.lbl.gov/MicroWorlds/ALSTool/EMSpec/EMSpec2.html (Last visited: Aug 12, 2011)

Last updated: Oct 10, 2011

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