Ionising Radiation

Aim: To investigate how radiation type, absorber thickness and distance affect the measured count rate.

1. Select No absorber and start counting to measure the background count rate before adding any source.
2. Select a radiation source and record the count rate at a fixed distance with no absorber in place.
3. Choose an absorber material and increase its thickness in steps, recording the count rate at each thickness until the radiation is mostly stopped.
4. Repeat for the other two radiation sources, using the absorber and thickness needed to stop each one, and compare the results in your table.
5. With no absorber, vary the distance between source and detector and record how the count rate changes.
6. For each source, which absorber and thickness combination stopped it most effectively, and how does this relate to the penetrating power of alpha, beta and gamma radiation? How does your distance data compare with an inverse-square relationship?