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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
To effectively use a Geiger-Müller (GM) tube for comparing the count-rates from two different radioactive rocks, the teacher should follow these steps:
- Position the rocks: Place the radioactive rocks in front of or near the GM tube, ensuring they are not in the tube, and maintaining a safe distance between them to avoid interference.
- Measure separately: Measure the count rate from each rock individually by using the GM tube for each rock one at a time.
- Standardize the measuring time: Ensure each count takes place over the same predetermined time period to allow for accurate comparison.
- Consistent distance: Keep the source-detector distance constant for both rocks during the measurements.
- Account for background radiation: Take into account and measure the background radiation count to subtract from the readings of the rocks.
- Repeat and average: Repeat the readings for each rock multiple times and calculate the average to improve accuracy.
Step 2
Complete the graph on Figure 5.
Answer
To complete the graph accurately:
- Start with the initial count rate: Begin at 80 cpm at time 0 hours.
- Apply the half-life decay: Given the half-life of 6 hours, the count rate will halve every 6 hours, leading to subsequent values of 40 cpm at 6 hours, 20 cpm at 12 hours, and 10 cpm at 18 hours.
- Draw the graph: Connect these points smoothly to show a decreasing exponential trend on the graph.
Step 3