... the spontaneous disintegration of the nucleus of an atom by emission of particles. That emission is usually accompanied by electromagnetic radiation. The energy produced by radioactivity has important military and industrial applications. However, the rays emitted by radioactive substances can cause radiation sickness. Some of these substances must be handled with extreme care. These substances are called radioactive wastes.
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Radioactive Links

Radioactivity may be created artificially by bombarding the nuclei of normally stable elements in a particle accelerator.
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