Half Life
Physics: Cambridge International GCSE Supplement, topic 5.4.3
Half-Life
The half-life of a particular isotope is the time taken for half the nuclei of that isotope in any sample to decay. Activity of a radioactive substance is measured in Becquerels (Bq).
Half-lives are predictable
- The radioactive decay of an individual atom is random and unpredictable.
- However, large groups of nuclei do normally behave in predictable ways.
Half lives are constant
- The half-life is the average time taken for the number of radioactive nuclei to halve.
- The half-life for any one isotope of an element is constant.
- The half-life of unstable isotopes can be seconds or millions of years.
Test yourself on Half Life
Which is true of the half life of a radioactive element?
How can the radioactive decay of an individual atom be predicted?
What range of values can a half life take?
Does a substance's mass halve over a half-life?
A sample contains 1kg of Uranium. After 1 half-life, what will be the approximate mass of the sample?