radioactivity
radioactivity
noun
noun
- [mass noun]the emission of ionizing radiation or particles caused by the spontaneous disintegration of atomic nuclei
放射性；放射现象
■radioactive substances, or the radiation emitted by these
放射物（或其辐射） - There are three main types of radiation emitted by radioactive substances: alpha particles (helium nuclei), beta particles (fast-moving electrons), and gamma rays (high-energy electromagnetic radiation). Naturally occurring radioactive elements such as uranium and thorium are a major source of heat in the earth's interior and of background radiation on the surface. Radioactivity is also released in nuclear explosions and in the waste products of nuclear reactors, and severe damage can be caused to living tissue by dosages which significantly exceed the natural background radiation
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