Physics · Grades 9–12
Half-life: a statistical model · Revision sheet
Apply repeated halving without predicting an individual decay time.
Learn the idea
Half-life
After one half-life the expected undecayed amount is half the initial amount in a large ensemble.
Repeated intervals
After n half-lives the expected fraction is (1/2) to the power n, not 1/(2n).
Random events
Individual nuclear decay times are random. Half-life describes population behaviour.
Safety scope
Use supplied numbers or simulations only. No radioactive-source handling activity is part of this material.
Explain without looking
- The expected remaining amount is 250 after two half-lives. Find the starting amount.
- Explain why a small sample need not show exactly half its nuclei remaining after one half-life.
Further reading and review references
These are reference links, not copied exercises, institutional endorsement or proof of independent review.
Independent educational review required. Grade bands are approximate; these are not officially aligned curricula.