Physics·Nuclear Physics · NSSCO 6.2.4-6.2.5
Radioactive decay & half-life
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Unstable nuclei fire out radiation to become stable — and they do it randomly, yet with a beautifully predictable rhythm. Here we write simple alpha and beta decay equations (watching how A and Z change), meet activity and the becquerel, define half-life, read the decay curve, and practise the three kinds of half-life calculation. We finish with the real-world uses — carbon dating, medical tracers and treatment, thickness gauging and smoke alarms — and the safety rules that go with them.
What you'll learn in this lesson
By the end you should be able to (NSSCO Physics 6.2.4-6.2.5):
- State what radioactive decay is and that it happens randomly and spontaneously
- Use activity, measured in becquerels (Bq), as the number of decays per second
- Give simple nuclide equations for alpha and beta decay and state how A and Z change
- Define half-life as the time for half of the radioactive nuclei in a sample to decay
- Read and use a decay curve, and find the fraction remaining after n half-lives as (½) to the power n
- Carry out simple half-life calculations — activity remaining, time taken, and the half-life itself
- Describe uses of radioactivity (carbon dating, medical tracers and treatment, thickness gauging, smoke alarms) and the safe handling of sources
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