Radioactivity

• Alpha particle:

  • Consists of two protons and neutrons
  • Identical to helium nucleus
  • Highest ionising effect
  • Least penertrating ability and can be absorbed by piece of paper
  • Neucleon number decreases by 4 and proton number decrease by 2 during alpha decay
• Beta particles:

  • Is a fast moving electron ejected from radioactive nucleus
  • Medium ionising effect
  • Medium penerating ability that is blocked by aluminium of a few millimetres thick
  • Nucleon number remains the same, proton number decrease by 1 during beta decay
• Gamma rays:

  • electromagnetic radiation thats emitted by radioactive nucleus with excess energy
  • Lowest relative ionising effect
  • Highest penetrating ability and is only absorbed by lead wall of a few centimetres thick
• Sources of background radiation:

  • Artifical sources: X-rays, building materials, waste product from nuclear power stations
  • Natural sources: Rocks, Radon gas in air, bananas carrot and salts containing radioactive potassium 40
• Measuring ionising radiation:

  1. Remove all known radioactive sources
  2. Start the Geiger-Muller counter and stopwatch
  3. Stop the counter after 10 minutes and record number of counts
  4. Find number of counts per minute by dividing reading by 10
  5. Repeat measurements at least once and calculate average
• Half life curve: Is best fit as decay is a random and spontanuous process
• Nuclear fission:

  • Original atom splits into two atoms of different elements, releasing neutrons
  • Released neutrons are absorbed by other radioactive nuclei
  • The radioactive nuclei also splits to release neutrons, resulting in a chain reaction that releases large amounts of energy
• Nuclear fission:

  • Two nuclei fuse together to form a bigger nucleus
  • Large amounts of energy is released in the form of gamma rays
• Uses of radioactivity in damaging cells:

  • Beta particles released by iodine 131 is used to treat thyroid cancer by destroying cancer cells
  • Gamma rays from technetium 99 is used to detect tumours
  • Gamma rays are used in radiosurgery and the killing of microbes on food and medical equipment
• Use of radiation in decay:

  • Uranium 238 is used to estimate age of rocks
• Use of radioactivity in ionising effects:

  • Alpha particles released by Americium 241 is used in smoke detectors
  • Beta particles and gamma rays are used to measure thickness of materials
• Ways to limit contamination of radioactive substances:

  • Leave immediate area to avoid being contaminated
  • Remove outer layer of clothing to reduce risk of contamination
  • Wash all exposed parts with soap and water to remove radioactive material on skin
• Reducing exposure to radiation:

  • Experiments to be carried out quickly in designated locations
  • Use long tongs to remove sample to increase distance between source and living tissue
  • Use shielding such as lead lined suits to absorb ionising radiation
  • Store radioactive material in sealed container that absorbes radiation from the source