P7 - Nuclear Radiation

• Radioactive decay

  Random emission of radiation from the nucleus of an atom
• Types of nuclear radiation

  • Alpha
  • Beta
  • Gamma
• Gamma radiation

  Electromagnetic radiation from the nucleus
• Alpha radiation is the most ionising type of nuclear radiation
• Alpha radiation causes both the mass and charge of the nucleus to decrease
• Beta radiation does not cause the mass to change but does cause the charge of the nucleus to increase
• Gamma radiation does not cause a change in the structure of the nucleus when it is emitted
• Radioactive activity

  The rate at which a source of unstable nuclei decays
• Unit to measure radioactive activity

  Becquerel (Bq)
• Count rate

  Number of decays recorded each second (by a detector, eg, Geiger-Muller tube)
• Half-life

  The time taken for half the unstable nuclei to decay, or the time taken for the count rate to halve
• Irradiation

  Exposing an object to nuclear radiation
• Radioactive contamination

  Unwanted presence of substances containing radioactive atoms on or in other materials
• What is the range in air of alpha, beta, and gamma radiation?

  Alpha - A few cm

  Beta - 1m

  Gamma - Unlimited
• Which materials can stop alpha, beta, and gamma radiation?

  Alpha - Sheet of paper

  Beta - Thin aluminium sheet

  Gamma - Thick lead/concrete