Science
What is Half-life?
A half-life is the time it takes for half of a radioactive substance to decay. After one half-life, half remains; after two, a quarter; and so on. Each element has its own fixed half-life, which scientists use for dating and in medicine.
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Watch a 2-minute lesson with voice + animation that explains half-life.
Key things to understand
- 1It's the time for half a substance to decay.
- 2Each radioactive element has a fixed half-life.
- 3After each half-life, half of what's left decays.
- 4It's used in carbon dating and nuclear medicine.
Frequently asked questions
- What is a half-life?
- The time it takes for half of a radioactive sample to decay into something else.
- How does half-life work over time?
- Each half-life halves what remains: 100% → 50% → 25% → 12.5%, and so on.
- What is half-life used for?
- Radiometric dating of ancient objects, nuclear power, and timing doses in medicine.