Measuring Half Lives
Physics: AQA GCSE Higher, topic 4.2.17
Measuring Half-Life
To find the half-life of a radioactive isotope, we must strip out the background radiation of the environment around us.
Calculation
- The level of radiation due to substance = level of radiation with substance and background radiation - level of background radiation.
Equipment
- We can work out the level of background radiation using a Geiger counter.
Half-Life
The half-life is the average time taken for the number of radioactive nuclei to halve. The 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 isotope of an element is constant.
- The half-life of unstable isotopes can be seconds or millions of years.
Test yourself on Measuring Half Lives
If the background count rate is 85, and the initial count rate is 1065, what is the count rate at the half-life?
How would you measure count rate to work out a substance's half-life?
If the background count rate is 100, and the initial count rate is 2000, what is true?
Does a substance's mass halve over a half-life?
Which is true of the half life of a radioactive element?