Overview

Calculate remaining quantity over time using radioactive half-life. Applicable to radioactive decay, drug metabolism, carbon dating, and any exponential decay phenomenon.

Formula

Remaining: N(t) = N₀ × (1/2)^(t/t₁/₂)
Remaining: N(t) = N₀ × e^(-λt)

Decay constant: λ = ln(2) / t₁/₂ ≈ 0.693 / t₁/₂

N₀ = Initial quantity, N(t) = Remaining after time t
t₁/₂ = Half-life, λ = Decay constant

How to Use

1. 1Enter the initial quantity (N₀).
2. 2Enter the half-life (t₁/₂).
3. 3Enter the elapsed time (t).
4. 4Remaining and decayed quantities are calculated automatically.

Tips

• ✔After 1 half-life: 50% remains, 2 half-lives: 25%, 3 half-lives: 12.5%.
• ✔Carbon-14 has a half-life of ~5,730 years, used in archaeological dating.
• ✔Iodine-131 has a half-life of ~8 days, important in medical applications.
• ✔Biological half-life of a drug is the time for its concentration in the body to halve.

FAQ