Physics lab
Solve half-life, time, initial quantity, or remaining quantity for a decaying material. Convert between half-life, mean lifetime, and decay constants. Includes the same formulas and derivations you'd find on calculator.net.
Enter any three values to compute the fourth.
Half-life is the time required for a substance to decay to half its initial value. It is often used for radioactive decay, biological decay, and pharmacology. Exponential decay can be described using:
Where N₀ is initial quantity, N(t) remaining, t is time, t₁/₂ is half-life.
For a fossil containing 25% of the carbon-14 of a living sample:
N(t) = N₀ (½)^(t/t₁/₂) ⇒ (¼) = (½)^(t/5730) ⇒ t = log(¼)/log(½) × 5730 ≈ 11,460 years.
Using the exponential forms, we can derive: