Radiation was initially classified as alpha, beta and gamma to distinguish between their different properties.

 Now we know that these particles are actually helium nuclei, electrons and photons. Is it time to drop the Greek labels?

Get the basics

Detecting radiation - the ionisation chamber

Radioactive isotopes release alpha, beta and gamma particles. These ionise a gas by knocking electrons off the atoms. This makes the gas able to conduct electricity, which can be used to detect the particles.

Penetrating power

Ionising radiation is stopped by the following materials:

  • alpha - paper
  • beta - aluminium
  • gamma - lead

Stretch for 7

Alpha radiation

Alpha particles are helium nuclei. Alpha radiation results in the loss of 2 protons and 2 neutrons.

Beta radiation

Beta radiation is the electrons released when neutrons change to protons.

Gamma radiation

Gamma radiation consists of high-energy photons.


The energy spectrum of beta particles indicates that they have a continuous spread of possible energies. This means that there must be another particle sharing the energy: the neutrino.

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