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What is a Half-Life?

All radioactive material becomes less radioactive over time. The activity of a radioactive source refers to the number of atoms of that source that decay every second. The time that it takes a source to lose half of its activity is known as that source's half-life.

Each radioactive isotope has its own specific half-life that never changes, regardless of the quantity or form of the material. Half-lives can range from microseconds to millions of years. Radon 220 has a half-life of approximately 3.8 days, while the half-life of Radium 226 is approximately 1,620 years.


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