GCSE Combined Science (AQA)

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Radioactive Activity

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Atomic structure Atoms and nuclear radiation

Radioactive Activity

3:11 Radioactive Acivity
Spec 4.4.2.1
Previous Unstable Nuclei Next Ionisation
  • Activity is the rate of nuclear decay in a sample with unstable nuclei.
  • Nuclear decay is random and not evenly spread over time.
  • Activity is best measured over long periods or with large numbers of decays to reduce variation.
  • Activity is measured in becquerels (Bq), where one Bq equals one decay per second.
  • Activity can be calculated by dividing the number of decays by time.
  • The activity of a sample depends on the isotope and sample size.
  • Radioactivity is detected using a Geiger-M��ller tube (GM tube).
  • GM tube has a clicker dial and a tube directed at the radioactive source.
  • Common radioactive sources include radium, uranium, and plutonium.
  • Safety measures include keeping a safe distance, wearing protective clothing, and storing the source after measurement.
  • The Geiger-M��ller tube clicks when radiation is detected.
  • Count rate is the number of nuclear decays detected per second by the GM tube.
  • Count rate is calculated by dividing the number of counts by time.
  • Longer counting periods lead to more accurate count rates.
  • Count rate is less than the actual activity because the GM tube detects only some of the radiation.
  • Radiation is emitted in all directions, but only a small amount is measured.
  • Count rate helps calculate activity, but detailed knowledge is not required for exams.
  • Background radiation can contribute to counts, which should be checked.

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