PhysicsChapter 12: Nuclear Physics
Half-Life
Introduction
The half-life of a radioactive isotope is the time taken for the number of undecayed radioactive nuclei, or the activity of a sample, to fall to half its initial value.
Definition
Example
Suppose the initial activity is: 800 Bq After one half-life: 400 Bq After two half-lives: 200 Bq After three half-lives: 100 Bq
General Pattern
After `n` half-lives: **Remaining fraction = (12)ⁿ**
Important Idea
Half-life does not mean every nucleus survives for exactly half that time. It is a statistical property of a large population.
Uses of Half-life
Half-life helps scientists: estimate how quickly radioactive materials decay; select isotopes for medical and industrial applications; * estimate the age of certain materials using suitable radioactive dating methods.
Exam preparation
Exam Focus
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Review the key facts, formulas and checks before you move on.Half-Life
Sticky Notes · Quick Revision
HALF-LIFE
- 100% → 50% → 25% → 12.5%
60-second revision
- 1 half-life → 12 remains.
- 2 → 14.
- 3 → 18.
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