Particle, alpha
A tiny mass of material composed of two protons and two neutrons. Alpha particles do not travel very far from their radioactive source. They cannot pass through a piece of paper, clothes or even the layer of dead cells which normally protects the skin. Because alpha particles cannot penetrate human skin they are not considered an "external exposure hazard." This means that if the alpha particles stay outside the human body they cannot harm it. However, alpha particle sources located within the body may pose an "internal" health hazard if they are present in great enough quantities. For instance, the risk from indoor radon gas is due to inhaled alpha particle sources which irradiate lung tissue. Alpha rays are streams of alpha particles.

Medical dictionary. 2011.

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  • alpha decay — Physics. a radioactive process in which an alpha particle is emitted from the nucleus of an atom, decreasing its atomic number by two. [1935 40] * * * Type of radioactive disintegration (see radioactivity) in which some unstable atomic nuclei… …   Universalium

  • alpha particle — noun a positively charged particle that is the nucleus of the helium atom; emitted from natural or radioactive isotopes • Hypernyms: ↑particle, ↑subatomic particle * * * ˈalpha particle [alpha particle] noun ( …   Useful english dictionary

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  • Alpha (letter) — Alpha (uppercase Α, lowercase α; el. Αλφα) is the first letter of the Greek alphabet. In the system of Greek numerals it has a value of 1. It was derived from the Phoenician letter Aleph .In both Classical Greek and Modern Greek, alpha represents …   Wikipedia

  • alpha particle — n. a positively charged particle given off by certain radioactive substances: it consists of two protons and two neutrons (a helium nucleus), and is converted into an atom of helium by the acquisition of two electrons …   English World dictionary

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