Half-life
ScienceDefinition
The time required for half of a radioactive substance to decay into a different element or isotope. After each half-life, the remaining amount of the original substance is reduced by 50%. Half-life is constant for any given isotope regardless of conditions.
Examples
- Carbon-14 has a half-life of 5,730 years, used to date archaeological artifacts
- Uranium-238 has a half-life of 4.5 billion years, used to date rocks
- Iodine-131 has an 8-day half-life, used in medical thyroid treatments
Key Fact
After n half-lives, remaining amount = initial amount × (1/2)ⁿ
Study This Concept
Practice half-life with free review games in these units: