The law says that no-one under the age of 16 can handle
radioactivesubstances, so the practical side of the experiment must
be carried outby the teacher.
The Geiger counter (made of the Geiger-Muller tube connected to
anelectronic counter) detects ionising radiation. The higher the
count, themore ionising radiation there is.
The aim of the experiment is to find out which material is the
bestabsorber of ionising radiation.
1. Measuring the Background Radiation Count
There is always background radiation around. To do the
experimentproperly, we need to subtractthe background count from
all themeasurements.
Count Time in seconds Background countrate in
Counts per second
13 30 0.4
to counter
Geiger-Mullertube
8/9/2019 Ionising Radiation Experiment
2/2
2. Measuring the penetrating effect of ionising
radiation
Source
Type of
radiation Shield Count Time
Count
rate incps*
Corrected
countrate incps*
Americium-241
Alpha
(and some )
Air 241 10 24.1 23.7Paper 127 10 12.7 12.3ThinAluminium
71 10 7.1 6.7
Thick lead 6 10 0.6 0.2
Strontium-90
Beta
Air 4075 5 815.0 814.6Paper 2082 5 416.4 416.0Thin
Aluminium
157 5 31.4 31.0
Thick lead 2 5 0.4 0.0
Cobalt-60Gamma
Air 614 10 61.4 61.0Paper 490 10 49.0 48.6ThinAluminium
395 10 39.5 39.1
Thick lead 208 10 20.8 20.4
* cps = counts per second
1. Why is ionising radiation dangerous?2. List at least three of
the safety precautions taken when handling
radioactive materials.3. What does this experiment tell you
about radiation?4. What does this experiment tell you about
radiation?5. What does this experiment tell you about radiation?6.
Which is the least penetrating type of ionising radiation?7. Which
is the most penetrating type of ionising radiation?8. Why is it
necessary to work out a correctedcount rate?9. Write a report about
the experiment.
