Modelling Decay

• Define the activity of an unstable nucleus.

  Activity is the rate at which a source of unstable nuclei decays.
• What is the unit of radioactive decay?

  Becquerel (Bq).
• What is count-rate?

  The number of radioactive decays per second for a radioactive source.
• Give an example of a detector that may be used to measure count-rate.

  Geiger-Muller tube.
• Describe the nature of radioactive decay.

  Random. Which nuclei decays and when is determined only be chance. It is possible to predict which nuclei will decay and when.
• Define the half-life of a radioactive isotope.

  The time it takes for the number of unstable nuclei in a substance to halve. The time it takes for the count rate from a sample to fall to half its initial level.