MYP Physics · 17 · data analysis
Does this source decay over the interval?
Atomic and nuclear physics · Original GioPhysics question with a detailed, mark-by-mark answer guide.
- Demand
- demanding
- Marks
- 8
- Topics
- 2
- Answer
- Complete
Question8 marks
A teacher supplies averaged detector rates, so fractional counts/min are possible. A separate background run gives a constant mean 15 counts/min. The source-plus-background (time in min, mean rate in counts/min) pairs are (0, 415), (10, 414), (20, 416), (30, 415). A student claims half-life = 10 min. Subtract background, test the claimed model against every reading, and calculate the model's expected total rate at 40 min. Use agreement within 5% of the predicted net rate as a classroom comparison rule. Explain one limitation of this test. No radioactive source is handled by students.
Task interpretation
What a complete response should do
Identify the useful evidence, process it with units, and make only the conclusion the data supports.
Split the problem into linked stages and state why each relationship applies.
- Response type
- data analysis
- Allocation
- 8 marks
- Demand
- demanding
Recorded total detector rate
Supplied source-plus-background mean rates; the graph does not pre-subtract background.
Vertical axis (y): Mean detector rate (counts/min)
Horizontal axis (x): Time (min)
Read the exact data as a table
| Time (min) | Mean detector rate (counts/min) |
|---|---|
| 0 | 415 |
| 10 | 414 |
| 20 | 416 |
| 30 | 415 |
These are the supplied values, not a worked answer. Lines join the supplied values; they are not a fitted model.
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Your self-assessment
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