Decay

• An alpha particle (α) consists off 2 neutrons and 2 protons.

  • Most ionising
  • Least penetrating
  • Blocked by a thin sheet of paper

  
• A beta particle (β) consists of 1 electron

  • Blocked by atleast 3mm of aliminium foil
• A gamma ray (γ) have no mass or charge at all

  • Least ionising
  • Most penetrating
  • Blocked by thick lead
• An electron can be excited to a higher energy level if it absorbs an electromagnetic radiation with the right amount of energy
• An electron can be deexcited to a lower energy level if it emits an electromagnetic radiation with the right amount of energy
• The half life of a source is the average time taken for half its nucleus to decay
• Irradiated = to be exposed to a radioactive source
• Contaminated = to have been made impure due to exposure to a radioactive source
• Which radiation is most dangerous

  Outside the body:

  • Beta
  • Gamma

  Inside the body:

  • Alpha
• What actions did the teacher take to avoid the risk connected with radioactive sources

  • No physical contact with the source
  • The source was held in a thick lead casing
  • Didn't point the source at anyone
  • Safety goggles
  • Hair tied back
  • Didn't have the source out for too long
• radiotherapy - the treatment of cancer using radiation


  • Gamma rays are focused on the tumour using a narrow beam (High doses of radiation kill living cells)
  • The beam is rotated round the person with the tumour at the centre
  • This minimises the exposure of normal cells to radiation, minimising the damage to healthy tissue
  • The treatment is given in doses with time between for the healthy cells to be repaired
• radiotherapy - the treament of cancer using radiation

  1. Implants containing beta-emitters are placed next to or inside the tumour
  2. Beta particles damage the tumour, but limit damage to the healthy cells surrounding it
  3. An implant with a long half life should be removed to stop the radiation from killing healthy cells once the cancerous cells are dead