Radiation

Article By:

Baird, Christopher S. Department of Chemistry and Physics, West Texas A&M University, Canyon, Texas.

Last reviewed:December 2019

DOI:https://doi.org/10.1036/1097-8542.566300

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• Radiation, published June 2019:Download PDF Get Adobe Acrobat Reader
• Radiation, published January 2014:Download PDF Get Adobe Acrobat Reader

The emission and outward propagation of energy-carrying particles or waves; also, the emitted particles or waves themselves. Radiation is a common phenomenon that transfers energy, matter, momentum, and information from one place to another. The major types of radiation are electromagnetic radiation (Fig. 1), particle radiation, acoustic radiation, and gravitational radiation. Generally speaking, any particle or wave can become radiation if it is emitted from a source and then propagates directly away from its source. In science, the word “radiation” is used in this general sense and does not necessarily imply that the particle or wave is harmful. Radiation that is directly harmful is referred to as ionizing radiation. Only ionizing radiation can, depending on the exposure, directly cause radiation sickness, mutation, and cancer. Radiation tends to travel in straight lines through space as it propagates away from its source. Radiation continues to propagate in this way until it encounters and interacts with a physical object. Through this interaction, the radiation can transfer to the object some or all of its energy, matter, momentum, or information. In the situation where all of the radiation is traveling generally in the same direction, the radiation is referred to as a beam. For instance, the radiation from a laser is known as a laser beam. Similarly, the radiation from a proton accelerator is known as a proton beam. See also: Electromagnetic radiation; Energy; Laser; Matter; Momentum

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