How Long Does Radiation Last?


Quick Answer

Radiation is emitted as an unstable atom decays to become a lighter element. Radiation, therefore, persists for as long as the unstable isotope remains present. Unstable isotopes emit radiation only once per decay, though they can decay several times.

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How Long Does Radiation Last?
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Full Answer

The persistence of radiation depends on the time it takes for an unstable isotope to decay. Different isotopes have different half-lives, which is the time it takes for 50 percent of a sample to decay. For example, carbon-11 is so unstable that it has a half-life of only 20 minutes, while the half-life of tellurium-128 is over 2 septillion years. Isotopes that decay in this manner are called radioactive isotopes.

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