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Properties of Alpha, Beta & Gamma Radiation

Alpha, beta and gamma radiation are produced when a nucleus decays. Their properties are summarised in the following table.

Property

Alpha

Beta

Gamma

Nature

Helium Nucleus - two protons and two neutrons

Fast moving electron

Energetic photon

Effect on photographic film

Yes

Yes

Yes

Approximate number of ion – pairs produced in air per mm

1

Typical material needed to stop it

0.01 mm thickness of aluminium

Piece of paper

Few cm air

A few mm aluminium

10 cm lead

Penetration ability

Low

Medium

High

Typical path length in air

A few cm. Alpha particles have the important property that most energy is lost at the end of the path - this is useful in the treatment of cancer.

Less than 1 m

Infinity

Deflection by magnetic or electric fields

Deflected since positively charged

Deflected since negatively charged

No deflection

Speed

About

Aboutbut very variable

Typical energy, eV

About 5 MeV

A few KeV to a few MeV

A few keV

Mass, kg

0

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