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2. Figure 3 shows a Geiger-Müller (GM) tube used for measuring radioactivity - Edexcel - GCSE Physics Combined Science - Question 2 - 2018 - Paper 1
Question 2
2. Figure 3 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-r... show full transcript
Worked Solution & Example Answer:2. Figure 3 shows a Geiger-Müller (GM) tube used for measuring radioactivity - Edexcel - GCSE Physics Combined Science - Question 2 - 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
To compare the count-rates from two different radioactive rocks using a Geiger-Müller (GM) tube, the teacher should follow these steps:
- Position both rocks at an equal distance from the GM tube to minimize variances caused by distance.
- Measure the count rate for each rock separately, recording the data clearly for comparison.
- Ensure that both measurements are taken over the same time period, such as one minute, to maintain consistency.
- Keep the distance of the GM tube from the rocks the same for both counts to ensure fair testing.
- Take into account or measure any background radiation to adjust the readings appropriately.
- Repeat the readings multiple times to calculate and report average count rates for both rocks.
Step 2
Complete the graph on Figure 4, as accurately as possible, to show how the count-rate from this isotope will change from the time of the first measurement.
Answer
The graph should start at the initial count rate of 80 cpm at time = 0. After the first half-life (6 hours), the count rate will drop to 40 cpm. Following the second half-life (12 hours), the count rate will decrease to 20 cpm. Finally, after the third half-life (18 hours), the count rate will reach 10 cpm. The graph should illustrate a smooth, decreasing curve passing through these points - (0,80), (6,40), (12,20), and (18,10).