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GCSE Questions: Radioactivity

Q17. A teacher demonstrates properties of radioactive particles by performing an experiment about radioactivity in class.

She demonstrates how different types of radiation are absorbed by putting different barriers between the source and the Geiger-Müller tube.

She uses four different radioactive sources, which she calls A, B, C and D in the experiment.

(a) Suggest two safety precautions that the teacher should use when performing this experiment to a class.

[2 marks]

(b) The teacher selects source A to investigate first. She uses the Geiger-Müller tube to measure the count rate (counts per minute) for different barriers. She then repeats the experiment with source B, source C and then source D.

Here are the results.

Source
 Count rate using different barriers
Paper
Aluminium
Lead
No barrier
A
113
112
22
112
B
20
21
20
182
C
162
23
21
164
D
282
78
24
280

 

He also finds that the average count rate with no sources and no barriers is 20.

(i) Which source A, B, C or D emits gamma radiation only? Explain your answer.

[2 marks]

(ii) Which source A, B, C or D emits alpha radiation only? Explain your answer.

[2 marks]

(iii) Which source A, B, C or D could emit both beta and gamma radiation? Explain your answer.

[2 marks]

(c) The teacher notices that the count rate behind the lead barrier ranges from 20 to 24.

Give two reasons why there are a wide range of results around 22 counts per minute.

[2 marks]

(d) The teacher decides to repeat the experiment. This time she records the number of counts for a much longer time interval for each source. Explain why this is an improvement to the experiment.

[2 marks]

(Total 12 marks)