Half-life & radioactive decay
Half-life (t½) is the time required for half of a radioactive substance to decay. It's a fundamental concept in nuclear physics, medicine, and archaeology.
N(t) = N₀ × e^(−λt)
λ = ln(2) / t½ (decay constant)
t = −ln(N/N₀) / λ (time elapsed)
Common half-lives
| Isotope | Half-life | Use |
|---|---|---|
| Carbon-14 | 5,730 years | Archaeological dating |
| Uranium-238 | 4.47 billion years | Geological dating |
| Iodine-131 | 8 days | Medical thyroid treatment |
| Radon-222 | 3.8 days | Home air quality concern |