Radiation Sources

Ionizing Versus Nonionizing Radiation

Electromagnetic radiation can be described by either its frequency f, its wavelength λ, or its photon energy E. Wavelength is the distance between successive peaks or troughs of a wave and is inversely proportional to frequency. The higher end of the electromagnetic spectrum has very short frequencies on the scale of the size of atoms, and this end of the electromagnetic spectrum has the highest energy, while longer frequencies have lower energies.

There are two distinct types of radiation, nonionizing radiation, which is the type of radiation emitted by light sources, radio transmitters, and microwaves, to name but a few sources. These come from the lower end of the electromagnetic spectrum and have insufficient energy to ionize—which can potentially damage human health.

Nonionizing radiation does not have enough energy per quantum to ionize target atoms or molecules, and as such it can only excite electrons to higher energy states. Nonionizing radiation can cause some health effects, however. Some nonionizing radiation can cause thermal heating of the skin and body, resulting in burns or thermal damage. Furthermore, exposure to high levels of light in the optical portion of the electromagnetic spectrum can cause damage to the eye or blindness.

Ionizing radiation is different in that it can produce ions, which are charged particles. It does this by detaching electrons from atoms or molecules—this process is called ionization, and it is relevant in sustainability terms, as ionizing radiation in sufficient doses has the potential to damage human health. Ionizing radiation must have a sufficiently high energy to be able to interact with the atoms of a target.

This rest of this article will concentrate on ionizing radiation, as it has greater potential to impact human health.

Ionizing Radiation Particles

Sources of Ionizing Radiation

Radiation sources can be divided into natural and man-made. We call the radiation that we receive through exposure to a variety of different radiation sources in everyday life background radiation. At sea level, the average background radiation is 26mrem (millirems). There are also man-made sources of radiation that are used for a variety of industrial, scientific, medical, and energy generation uses.

Types of Ionizing Radiation