Nuclear radiation

• What is radioactive decay?

  random emission of radiation from the nucleus of an atom
• What are the three types of radiation?

  alpha, beta, gamma
• Gamma radiation

  electromagnetic radiation from the nucleus
• Alpha radiation

  two protons and two neutrons (like Helium nucleus)
• Beta radiation

  fast moving electron
• Which radiation is the least ionising?

  gamma
• what stops alpha radiation?

  sheet of paper
• what stops beta radiation

  few mm of aluminium
• what stops gamma radiation

  several cm of lead or thick concrete
• which type of nuclear radiation is the most ionising?

  alpha
• what is radioactive decay?

  rate at which a source of unstable nuclei decays
• what unit is used to measure the activity of a radioactive source

  becquerel (Bq) = 1 decay per second
• what is the half-life of a substance

  time for half the number of unstable nuclei to decay OR time for the count rate to halve
• how far does alpha radiation travel in air?

  a few cm in air
• how far does beta radiation travel in air?

  1m in air
• how far does gamma radiation travel in air?

  unlimited range in air