Ei-9 Properties of Radiation
Published: Tuesday 05 June 2007 - Updated: Tuesday 29 March 2011
To demonstrate the penetrating power of Alpha, Beta and Gamma-rays
- Geiger tube
- Cs137 source
- Retort stand
- Aluminium foil
- Lead blocks
Click on pictures to enlarge.
A commercial smoke alarm contains a weak Americium source which emits alpha particles. A single sheet of paper interposed between the source and detector reduces the count rate dramatically showing the weak penetrating power of alpha particles.
A Cs137 source emits both beta particles and gamma rays.
The same sheet of paper has little effect on these emissions but a thin sheet of aluminium will stop the beta particles. These particles may be shown to be electrons by deflecting them with a strong magnetic field. The gamma rays require a substantial thickness of lead to reduce the count rate.