Types of Radiation

Using radiation offers many societal benefits, but what is radiation exactly? The term radiation covers a lot of things, but they are not all the same. When someone mentions the word radiation, we might think of the big mushroom cloud from a nuclear weapon explosion, the microwaves in our microwave oven, how our cell phones work, getting a suntan in a tanning salon, having a chest x ray, or nuclear power plants. In the broad category of radiation, the broad definition includes all of those things and more.

We need to narrow that broad definition of radiation to talk about the type of radiation that is the focus of information on this site. Radiation is energy in the form of waves (beams) or particles. Radiation waves are generally invisible, have no weight or odor, and have no positive or negative charge. Radioactive particles are also invisible, but they have weight (which is why they are called a particle) and may have a positive or negative charge. Some radiation waves can be seen and felt (such as light or heat), while others (such as x rays) can only be detected with special instrumentation.

X rays, gamma rays, alpha particles, and beta particles are ionizing radiation. Ionizing radiation has a lot of energy that gives it the ability to cause changes in atoms—a process called ionization. Radio and TV signals, microwaves, and laser light are nonionizing types of radiation. Nonionizing radiation has less energy than ionizing radiation. When nonionizing radiation interacts with atoms, it does not cause ionization (hence nonionizing or not ionizing). It is important to understand what is and isn’t ionizing radiation so you can better understand what the potential health effects might be. While the primary focus of this Web site is ionizing radiation, we have included a brief section on nonionizing radiation sources to help learn what they are so we don’t confuse them with ionizing radiation sources.