Radioactivity

Radioactivity

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Observing nuclear radiation

  • The nuclei of radioactive substances are unstable
  • Become stable by radioactive decay
  • To do this, they emit radiation and turn into other elements
  • Three types of radiation emitted are: alpha particles, beta particles & gamma rays
  • Radioactive decay is a random process and is not affected by external conditions
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Alpha Beta and Gamma radiation

  • An alpha particle is a helium nucleus made up of 2 protons and 2 neutrons - relatively large, lots of collisions with atoms and strongly ionised. Because of the collisions, they don't penetrate far into the material.
  • A beta particle is a high speed electron from the nucleus - emitted when a neutron changes to a proton and an electron - much smaller and faster and can penetrate further into material but are blocked by a few metres of air or a thin sheet of aluminium.
  • Gamma radiation is very short wave length electromagnetic radiation that is emitted from the nucleus - will travel a long way through material before colliding with an atom so several cms of lead or concrete are needed to absorb the radiation. Gamma rays are not deflected by electric or magnetic fields.
  • 'Ionisation' - when nuclear radiation travels through a material knocking electrons off, creating ions
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