Penetrating properties of radiations

The different types of radiation are often compared in terms of their penetrating power, their ionising power and how far they can travel in the air.

SymbolPenetrating powerIonising powerRange in air
AlphaαSkin/paper High < 5 centimetre (cm)
Betaβ3 mm aluminium foil Low≈ 1 metre (m)
GammaγAt least 40 mm lead or 2 m concreteVery low> 1 kilometre (km)
Alpha, beta and gamma rays passing through a hand, beta and gamma rays passing through aluminium and gamma rays pass through lead.

One example of a use of alpha radiation is in smoke detectors. A source of alpha radiation is used because the range is very low and alpha radiation has a very high ionising power.