Calculate radioactive decay, half-life, remaining quantity, and elapsed time using the exponential decay formula. Used in physics, chemistry, medicine, and archaeology.
| Isotope | Half-life | Use |
|---|---|---|
| Carbon-14 (¹⁴C) | 5,730 years | Radiocarbon dating |
| Uranium-238 (²³⁸U) | 4.47 × 10⁹ years | Geological dating |
| Iodine-131 (¹³¹I) | 8.02 days | Medical therapy |
| Technetium-99m | 6.01 hours | Medical imaging |
| Potassium-40 (⁴⁰K) | 1.25 × 10⁹ years | K-Ar dating |
| Metric | Value |
|---|
| Half-lives elapsed | Time | Remaining % | Remaining qty |
|---|
The half-life of a radioactive isotope is the time required for half of the atoms in a sample to decay. The decay follows an exponential law: N(t) = N₀ × (1/2)^(t/t½).
| Unknown | Formula |
|---|---|
| Remaining (N) | N = N₀ × (½)^(t/t½) |
| Time (t) | t = t½ × log(N/N₀) / log(½) |
| Half-life (t½) | t½ = t × log(½) / log(N/N₀) |
| Initial (N₀) | N₀ = N / (½)^(t/t½) |
Radiocarbon (¹⁴C) dating is used extensively in Australian archaeology to date Aboriginal artefacts and sites. The ANSTO (Australian Nuclear Science and Technology Organisation) facility at Lucas Heights operates one of Australia's nuclear reactors and produces medical radioisotopes including Technetium-99m for diagnostic imaging.