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 |
About |
|
|
Typical energy, eV |
About 5 MeV |
A few KeV to a few MeV |
A few keV |
|
Mass, kg |
|
|
0 |
but very variable
