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Figure 4 shows a Geiger-Müller (GM) tube used for measuring radioactivity - Edexcel - GCSE Physics - Question 3 - 2018 - Paper 1
Question 3
Figure 4 shows a Geiger-Müller (GM) tube used for measuring radioactivity. (a) Describe how a teacher should use a Geiger-Müller (GM) tube to compare the count-rate... show full transcript
Worked Solution & Example Answer:Figure 4 shows a Geiger-Müller (GM) tube used for measuring radioactivity - Edexcel - GCSE Physics - Question 3 - 2018 - Paper 1
Step 1
Describe how a teacher should use a Geiger-Müller (GM) tube to compare the count-rates from two different radioactive rocks.
Answer
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Place the rocks in front of or near the GM tube without letting them come into direct contact with the tube.
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Measure the count rate for each rock separately to ensure accurate readings.
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Ensure to measure each count for the same time period to maintain consistency in the data collected.
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Make sure the distance of the GM tube from the source is the same for both readings to eliminate distance-related discrepancies.
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Account for and measure the background count to subtract this from the measurements for each rock, ensuring only the counts due to the rocks are recorded.
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Repeat the readings multiple times and average the values to obtain reliable count rates for both rocks.
Step 2
Complete the graph on Figure 5...
Answer
To complete the graph for the radioactive isotope:
- Start from the first count rate of 80 cpm at time 0 hours.
- Given the half-life of 6 hours, after 6 hours the count rate would be half of 80, which is 40 cpm.
- Continue this process:
- 12 hours = 20 cpm
- 18 hours = 10 cpm
- 24 hours = 5 cpm
- Plot these points on the graph against the respective time to show the exponential decay of the count rate.