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Nuclear Science and Technology and How It Influences Your Life http://www.aboutnuclear.org/ |
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Radiation and Radioactivity |
Radiation refers to the propagation of waves and particles through space and includes both electromagnetic radiation and atomic and subatomic particle radiation. Electromagnetic radiation has a broad, continuous spectrum of energy (see The Radiation Spectrum) that includes visible light, radio waves, microwaves, x-rays, gamma rays, and infrared and ultraviolet radiation. All electromagnetic radiation travels at the speed of light. Particle radiation includes alpha and beta particles, neutrons, protons and heavy ions. The speed and energy of particle radiation depends upon the source of the radiation and any subsequent interaction of the particle with other matter.While there are many different sources of radiation, it generally arises from or is produced by radioactive decay, energy change of an atomic electron or nucleus, motion of atoms or molecules, or the interaction between particles or electromagnetic radiation and atoms or nuclei. There are many sources and types of naturally occurring radiation such as the sun, radioactive materials, visible light, solar and cosmic radiation, and thermal radiation (what is typically referred to as heat). Radiation can also be generated to diagnose and treat illness, eliminate or reduce harmful microorganisms to enhance the safety of medical equipment and the food supply, cook food, transmit information (radio, television, cellular phones, etc.), and many other applications addressed on this website. Radioactivity refers to the property of spontaneous emission of particles or electromagnetic radiation exhibited by certain materials. This radiation is emitted by unstable atoms as they undergo a transition to a more stable state; the transition is called radioactive decay. Unstable atoms that exist in nature are said to be naturally radioactive. Examples of radioactive atoms found in nature are carbon-14, potassium-42, radon-222, uranium-235, uranium-238 and thorium-232. In addition to naturally occurring radioactive materials, radioactive atoms can be produced when the nucleus of an atom is made to interact with a particle or electromagnetic radiation to form an unstable nucleus; this is typically done in nuclear reactors and particle accelerators. As radioactive atoms go through the transition to a stable state they emit radiation in several forms as follows:
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