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Radiation and Radioactivity : Types of Radiation : Alpha Particles |
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Alpha Particles |
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Alpha particles are composed of two protons and two neutrons emitted from an unstable atom. They travel at approximately 16,000 kilometers per second (about 36 million miles per hour) yet they can be stopped after traveling through: |
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3 centimeters (about 1.2 inches) of air,
0.2 millimeters (about 0.008 inches) of water, or a piece of paper or skin |
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Thus, their radiation only becomes effective if alpha particles are emitted from radioactive materials that have been ingested into the body, either in the lungs by inhalation, or in the blood through a cut. |
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