Nuclear Decay

• Alpha Particles

  • Helium Nuceli
  • Strongly Ionising
  • Charge of +2e
  • Low Penetrating Power
  • Stopped by Skin and Paper
• Beta Particles

  • Fast moving electrons
  • Charge of -e
  • Weakly Ionising
  • Greater penetrating power than alpha particles
  • Stopped by a few mm of aluminium
• Gamma Radiation

  • High frequency EM radiation
  • no charge
  • Very weakly ionising
  • High Penetration power
  • Intensity reduced by thick lead or concrete
• Penetration Power of Radiation

  Alpha: Stopped by paper

  Beta: Stopped by thin aluminium

  Gamma: Intensity reduced by thick lead and concrete
• Deflection of Radiation in Magnetic Fields

  Alpha: Deflected slightly

  Beta: Deflected greatly in the opposite direction to alpha

  Gamma: Unaffected
• Deflection of Radiation in Electric Fields

  Alpha: Deflected slightly toward the negatively charged plate

  Beta: Deflected greatly toward the positively charged plate

  Gamma: Unaffected
• Nuclear Decay is a spontaneous process where unstable nuclei decay to form more stable nuclei
• Alpha Decay

  • Alpha particles pass through an atom, knocking out electrons through electrostatic force
  • Each electron removed results in a loss of energy
  • Once an alpha particle runs out of energy, it attracts two electrons and becomes a helium nucleus
• Beta Decay

  • A neutron decays into a proton, releasing a fast moving electron
  • Most energy is lost in a single interaction with an electron
• Gamma Decay

  • Uncharged so, they must collide with an electron
  • Slower to lose their energy and will be lost in a single collision
  • Often accompanies other forms of decay
• Background Radiation

  Radiation present in the environment from sources such as rocks, food or space. This must be accounted for in calculations.
• Half-Life

  The time taken for the mass of the radioactive isotope to decrease by half of the initial mass
• Activity

  The number of nuclei of the radioactive isotope that disintegrates per second
• Decay Constant

  The probability of an individual nucleus decaying in a unit of time