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Radiation is one of the ways that energy travels through space or matter. Radiant energy is emitted as either electromagnetic waves or subatomic particles. This energy runs along a continuum on the electromagnetic spectrum on the basis of its wavelength, frequency, or energy. The two major types of radiation—non-ionizing and ionizing—are differentiated by the level of energy they emit. Lower wavelength, lower frequency waves contain less energy than higher wavelength, higher frequency waves.
Non-ionizing radiation is electromagnetic radiation that can move atoms around in a molecule or cause them to vibrate but does not possess enough energy to remove electrons from the outer shells of atoms. Non-ionizing radiation includes sound waves, visible light, and microwaves.
Ionizing radiation is electromagnetic radiation and subatomic particles that contain enough energy to break chemical bonds, strip away electrons, and create atoms that are ionized or charged. Ionizing radiation is given off by cosmic rays, X-ray machines, and naturally occurring or manmade radioactive materials.
The most common types of ionizing radiation are
- Alpha Particles
- Beta Particles
- Gamma Rays
- X-rays
These four types of ionizing radiation are distinguished by their abilities to penetrate materials, with alpha particles being the least penetrating and gamma rays and X-rays the most penetrating. Alpha or beta particles are emitted by unstable atoms as they disintegrate. Gamma rays are emitted from the nucleus of atoms following radioactive disintegration and X-rays are released when electrons strike a metal target.
Image courtesy of NASA.