Practise radiation practicals by choosing absorbers, measuring count rate, subtracting background and judging conclusions from data.
A teacher investigates the penetrating ability of the gamma rays from a gamma source.
This is the teacher's method.
- place the gamma source at a distance of 25 cm from a radiation detector
- place a 1 cm thick absorbing material between the source and the detector
- measure the radiation count from the source for a time period of 3 s
- calculate the count rate in counts per second
- repeat the measurement two more times
The teacher repeats this method for different absorbing materials.
State the independent variable in the teacher's investigation.
Explain why every absorbing material used in the investigation has a thickness of 1 cm .
Suggest one improvement the teacher could make to this method.
The table shows the teacher's results for seven different absorbing materials.
On the grid, plot a bar chart of the mean count rate for each absorbing material.
A student concludes that plastic is the best absorber of gamma radiation because plastic gives the largest mean count rate.
Evaluate the student's conclusion.