Radioactive decay and nuclear radiation

• • The nucleus of unstable isotopes give out radiation to become more stable
  • This is radioactive decay
• • Activity is the rate at which a source of unstable nuclei decays
  • Activity is measured in becquerel
• • An alpha particle is two neutrons and two protons
  • Dont penetrate far
  • Stopped by sheet of paper
  • Strongly ionising
• • A beta particle is high speed electron
  • Moderately ionising
  • Penetrate far
  • Stopped by sheet of aluminium
• • Gamma particles are electromagnetic waves
  • Penetrate far
  • Stopped by thick lead/concrete
  • Weakly ionising - pass through materials rather than collide with atoms
• • Alpha radiation is used in smoke detectors
  • Ionise air particles so current will flow
  • Smoke in air will bind to ions
  • Current stops and alarm sounds
• • Beta particles are used to test thickness of metal
  • Particles not immediately stopped by material like alpha radiation
  • Do not penetrate as far as gamma rays