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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
- The teacher should place the radioactive rocks in front of or near the Geiger-Müller tube but not inside it to avoid contamination.
- Measure the count rate for each rock separately to get accurate readings.
- Ensure each rock is measured for the same duration to maintain consistency in the readings.
- Keep the distance from the source detector to both rocks the same to ensure fairness in comparison.
- Account for any background radiation by taking an initial reading with no rock present, and subtract this from the rock counts.
- Repeat the measurements multiple times and take the average to reduce the impact of random fluctuations.
Step 2
Complete the graph on Figure 5.
Answer
To complete the graph:
- Start with the initial count rate of 80 cpm at time = 0.
- After 6 hours (1 half-life), the count rate will drop to 40 cpm.
- After 12 hours, the count rate will drop to 20 cpm.
- After 18 hours, it will be approximately 10 cpm.
- Continue this trend until the count rate approaches zero, ensuring the curve reflects exponential decay.
Step 3