School of Physics Lecture Demonstration Manual

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



Click on pictures to enlarge.

Radiation Setup pic


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.

Safety notes

Electrical Safety 

Radiation Safety 


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