Radioactive Decay
Start with a sample of undecayed nuclei — adjust the initial count and half-life to watch the population (and a grid of individual nuclei) decay exponentially.
Preview — sign up free to change the numbers yourself
What you can adjust
- Initial nuclei count (N0)
- 10 – 100000
- Half-life
- 1 – 20 s
How many undecayed nuclei you start with.
Time for half of the remaining nuclei to decay — the same fraction decays in every equal time interval, no matter how much is left.
About this simulation
What it shows
A sample of nuclei decays over time, shown as a grid of individual nuclei and as a count of those left. The count follows a smooth falling curve.
The key idea
Each nucleus has the same chance of decaying in any moment, so in every half-life half of what remains decays: N = N₀ (½)^(t/T½). The same fraction goes in each equal time interval, however much is left.
Try this
Raise Half-life from 4 s to 8 s: the decay takes twice as long, yet every half-life still halves the number of nuclei left.
Each nucleus's decay time is set so that the sample follows the exact curve. Real decay is random, so a small sample would wobble around it.