Summary:
- Radioactive materials lose some of their activity each time a decay event occurs.
- This loss of activity can be estimated by determining the half-life of an isotope.
- Half-life is defined as that period of time needed for one-half of a given quantity of a substance to undergo a change.
- Some isotopes have long half-lives – the half of U-234 is 245,000 years.
- Other isotopes are shorter – I-131 has a half- life of 8.02 days.