6.2.1 radioactive decay

• radioactive decay is random - we cannot predict when an individual atom will emit (produce) ionising radiation
• A nuclei can become more stable by decaying
• Some nuclei are unstable
• Radioactive decay is spontaneous (unpredictable)
• Fill the gaps

  A) alpha

  B) alpha decay

  C) helium nuclei

  D) beta decay

  E) electrons

  F) gamma decay

  G) high-energy

  H) electromagnetic wave

  I) frequency

  
• There are three types of ionising radiation

  • Alpha
  • Beta
  • Gamma
• there are three ways of determining radioactivity:

  • cloud chamber
  • photographic film
  • Geiger counter (Geiger-Muller tube)
• Detecting radioactivity - Cloud Chamber

  • full of air containing alcohol vapour
  • ionising radiation enters air, leaving trail of ionised air molecules
  • alcohol vapour condenses on the ionised air molecules, showing a trail of radiation
• Detecting radioactivity - Photographic film

  • ionising radiation has the same effect on photographic film as light
  • a bright spot appears wherever ionising radiation hits the film
• Detecting radioactivity - Geiger counter

  • ionising radiation enters tube of low pressure gases
  • ionises atoms in gas, knocking electrons out of atoms
  • gas can now conduct electricity and completes an electric circuit. current flows between electrodes
  • current produces a clicking noise
  • the count-rate is the number of decays recorded each second
• Count-rate = the number of decays recorded each second
• A cloud chamber is a container full of supersaturated alcohol vapour.
• In radioactive decay, we cannot predict when an individual atom will emit (produce) ionising radiation.