MYP Physics · 20 · investigation
Design a shielding comparison with background radiation
Independent assessment practice · Original GioPhysics question with a detailed, mark-by-mark answer guide.
- Demand
- discriminating
- Marks
- 9
- Topics
- 1
- Answer
- Complete
A school has a sealed low-activity source, a radiation detector, a stand, and equal-area sheets of paper, aluminium, and acrylic. Under approved supervision, students want to compare how the materials affect count rate. They must not handle the source directly.
- a
Formulate Write a focused research question and identify the independent and dependent variables.
3 marks - b
Design Describe a safe method that produces reliable, comparable data.
4 marks - c
Evaluate Explain why a result with aluminium lower than paper does not by itself identify the radiation or prove aluminium is always the best shield.
2 marks
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a
Formulate Write a focused research question and identify the independent and dependent variables.
Turn the task into a measurable method: name the independent, dependent and controlled quantities; describe apparatus and repeats; then explain how the evidence will be processed and how uncertainty or safety will be managed.
- 1
Writes a question comparing absorber material or controlled absorber thickness with corrected count rate.
- 2
Identifies absorber material or thickness as the independent variable.
- 3
Identifies background-corrected count rate as the dependent variable.
b
Design Describe a safe method that produces reliable, comparable data.
Turn the task into a measurable method: name the independent, dependent and controlled quantities; describe apparatus and repeats; then explain how the evidence will be processed and how uncertainty or safety will be managed.
- 1
Measures background for a sufficiently long fixed interval and subtracts it from each source-plus-background result.
- 2
Keeps source–detector distance, alignment, counting time, absorber area, and detector settings constant.
- 3
Repeats each condition in a varied or randomised order and calculates means with spread or uncertainty.
- 4
Uses the stand or tongs and follows local source rules to minimise time near the source, maximise distance when possible, and avoid direct handling.
c
Evaluate Explain why a result with aluminium lower than paper does not by itself identify the radiation or prove aluminium is always the best shield.
Turn the task into a measurable method: name the independent, dependent and controlled quantities; describe apparatus and repeats; then explain how the evidence will be processed and how uncertainty or safety will be managed.
- 1
Explains that source emission may be mixed and attenuation also depends on absorber thickness or mass per area, geometry, and detector response.
- 2
Explains that shielding choice also depends on radiation type, secondary radiation, required reduction, practicality, and safety context; one comparison cannot support a universal claim.
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