Types of radioactivity
There are three main types of radioactivity:
alpha (a) beta (b) gamma (g)
Property |
Alpha (a) |
Beta (b) |
Gamma (g) |
Range in air |
a few cm |
many cm |
metres |
Ionising ability |
large |
small |
very small |
Stopped by |
paper |
mm of aluminium |
cm of lead |
Charge |
+2e |
-e |
0 |
Mass |
8000m |
m |
0 |
Deflection by magnetic field |
a little |
a lot |
none |
Speed |
<1%c |
90%c |
c |
[m is the mass of the electron - about 10
-30 kg!]
[c is the speed of light, 300 000 km/s]
Experiments have identified the three types of radiation as:
Alpha – two protons and two neutrons (the nucleus of a helium atom)
Beta – high speed electrons
Gamma – very short wavelength electromagnetic radiation