4.2.2

Radioactive Decay 2

Test yourself

Detecting Radioactivity

There are three primary ways of detecting radioactivity.

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Geiger counter (Geiger-Muller tube)

  • Ionising radiation enters a tube full of low-pressure gases.
  • It ionises the atoms in the gas, knocking electrons out of the atoms.
  • The gas can now conduct electricity and completes an electric circuit. Current flows between electrodes.
  • The current produces a clicking noise.
  • The count-rate is the number of decays recorded each second.
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Photographic film

  • Ionising radiation has the same effect on photographic film as light.
  • A bright spot appears wherever the ionising radiation hits the film.
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Cloud chamber

  • A cloud chamber is a container full of air containing alcohol vapour.
  • Ionising radiation enters the air and leaves a trail of ionised air molecules.
  • The alcohol vapour condenses on the ionised air molecules, showing the trail of radiation.

Background Radiation

Unstable atoms (or isotopes) are very common. They even exist in our bodies. They decay radioactively and this means that we are always surrounded by background radiation.

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Rocks

  • Rocks like granite contain small amounts of uranium salts.
  • Over time, the uranium decays, releasing other radioactive nuclei.
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Food

  • Fruits high in potassium, like bananas, are very slightly radioactive.
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Radon

  • Radon is a gas that emits alpha particles.
  • If we breathe in alpha particles, alpha radiation will reach our lung tissue.
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The sun

  • The sun emits some ionising radiation

Jump to other topics

1Energy

2Electricity

3Particle Model of Matter

4Atoms & Radiation

5Forces

6Waves

7Magnetism

8Astrophysics

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