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2.8 understanding radiation


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2.8 understanding radiation

  1. 1. 2.8 Understanding radiation December 7, 2010
  2. 2. Key terms <ul><li>Nucleus : the inner part of the atom where protons and neutrons are found </li></ul><ul><li>Radiation : energy spreading out, as carried by electromagnetic radiation or a particle </li></ul><ul><li>Ionising radiation : radiation that can remove electrons from atoms, causing the atom to become positively charges </li></ul><ul><li>Non-ionising radiation : radiation that does not remove electrons from atoms (e.g. microwaves or infra-red) </li></ul>
  3. 4. Alpha ( α ) radiation <ul><li>Alpha radiation consists of α particles </li></ul><ul><li>These are He nuclei, each having two protons and two neutrons and a charge of +2 </li></ul><ul><li>When α particles hit other particles they knock electrons off them, this leaves the particles with a positive charge </li></ul><ul><li>The particles have been ionised </li></ul><ul><li>α particles are highly ionising </li></ul>
  4. 6. Penetration <ul><li>Alpha particles are large compared with beta and gamma so are much less penetrating </li></ul><ul><li>Only a few cm of air or a sheet of paper will stop them, they cannot get through out skin! </li></ul>
  5. 9. Beta ( β ) radiation <ul><li>Beta radiation consists of fast-moving electrons that have been given off by unstable nuclei </li></ul><ul><li>If they collide with an atom that can also knock off electrons and ionise the atom </li></ul><ul><li>They are small so are only moderately ionising </li></ul>
  6. 11. Penetration <ul><li>They are much smaller than alpha so much more penetrative </li></ul><ul><li>They can travel through a few mm of Aluminium before being absorbed </li></ul><ul><li>They are moderately penetrating so will go through your skin and are a danger to living organisms </li></ul>
  7. 14. Gamma ( γ ) radiation <ul><li>Gamma radiation is a type of electromagnetic radiation, it has a very short wavelength and is emitted from unstable nuclei </li></ul><ul><li>EM radiation has no charge so cannot readily ionise but due to its large energy can weakly ionise </li></ul><ul><li>Because it is weak it can travel through aluminium and several cm of lead </li></ul><ul><li>It will easily pass through the human body </li></ul><ul><li>It can also create Hulks </li></ul>
  8. 16. Using alpha <ul><li>Alpha radiation is used in smoke detectors. A weak source ionised the air and causes a small current to flow. If smoke gets into the detector the current is affected and the alarm goes off </li></ul>
  9. 17. Using beta <ul><li>Beta radiation is used to monitor the thickness of paper during production. A GM tube is used to monitor how much radiation gets through which changes the pressure on the rollers </li></ul>
  10. 18. Using gamma <ul><li>Gamm radiation is used to kill bacteria in food for long term storage. It is also used in the treatment of cancer </li></ul>
  11. 19. Questions <ul><li>Describe two properties each of alpha, beta and gamma radiation and an application of each </li></ul><ul><li>Describe the applications and dangers of radiation </li></ul>