Radiation transports energy. The energy is transported in the form of electromagnetic waves via photons (= light quanta/light particles), as with visible light, X-radiation or gamma radiation or as particle flow, as with alpha or beta radiation.

Depending on the effect of radiation on material, a distinction can be made between ionising and non-ionising radiation:

  • The energy of ionising radiation is sufficiently high that it can knock out electrons from the shell of the atom or molecule, leaving the atom or molecule with a net positive charge (at least for a short time).
  • Radiation with insufficient energy to ionise material is known as non-ionising radiation.

When ionising radiation hits living cells or organisms, these ionisation processes or other alterations in molecules can cause damage to cells and organisms.

Ionising radiation can be generated artificially (X-radiation) or occurs when certain atomic nuclei undergo radioactive decay (alpha, beta, gamma and neutron radiation). When atomic nuclei are split, for example in the fuel rods of a nuclear reactor, ionising radiation is generated in addition to the fission products.

Depending on the starting material, stable or radioactive decay products are formed, which can further decay.