Nuclear Radiation

• What happens to some atomic nuclei that are unstable?


  They give out radiation to become more stable.
• What determines the type of radiation emitted by an unstable nucleus?


  The reason for the nucleus's instability.
• Is it possible to predict exactly when an atom will decay?


  No, it is a random process.
• How is the activity of a radioactive source measured?


  In becquerels (Bq).
• What does one becquerel (1 Bq) represent?


  One decay per second.
• What is the count-rate in the context of radioactive decay?


  The number of decays recorded each second by a detector.
• What type of detector might be used to measure the count-rate?

  A Geiger-Muller tube.
• How is one becquerel (1 Bq) related to count-rate?


  One becquerel is equivalent to one count per second.
• Key Point

  A contaminated object continues to give out radiation until decontaminated.

  An irradiated object does not become radioactive.
• What are the three main types of nuclear radiation?

  Alpha, beta, and gamma
• What is the ionising power of alpha radiation?


  Alpha radiation has strong ionising power
• What can absorb alpha radiation?


  A few centimetres of air or a thin sheet of paper
• How does beta radiation's ionising power compare to alpha radiation?


  Beta radiation has reasonable ionising power
• What material can absorb beta radiation?


  A few millimetres of aluminium
• What is the ionising power of gamma radiation?


  Gamma radiation has poor ionising power
• What materials are needed to absorb most gamma radiation?


  Many centimetres of lead or many metres of concrete
• What do all three types of nuclear radiation have in common?


  They are all ionising and can knock electrons from atoms
• Which type of radiation is the most ionising?

  Alpha radiation
• Which type of radiation is the least ionising?

  Gamma radiation
• What is the composition of alpha radiation?


  Two neutrons and two protons, similar to a helium nucleus
• What happens to a neutron during beta decay?


  A neutron turns into a proton and emits a high-speed electron
• What is the nature of gamma radiation?


  Gamma radiation is electromagnetic radiation emitted from the nucleus
• How does gamma radiation interact with living cells?


  Gamma radiation is likely to pass through living cells without causing ionisation
• What is the fourth type of nuclear radiation?

  A neutron
• When can a neutron be emitted?


  During radioactive decay