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Home > Physics > Revision videos > Radioactive decay


Radioactive decay

Radioactive Decay

This video explains what ionising radiation is and how a radioactive substance decays over time according to its half-life.

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Key learning points:

  • An atom is made up of a small nucleus, containing protons and neutrons, which is surrounded by orbiting electrons.
  • The nucleus of a radioactive atom is unstable and will decay by giving out nuclear radiation.
  • There are three types of nuclear radiation: alpha particles, beta particles and gamma rays.
  • Nuclear radiation can remove electrons from atoms. This is called ionisation.
  • The activity of a radioactive source decreases with time.
  • The "half-life" of a radioactive source is the time taken for its activity to decrease to half its starting value.

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