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Figure 1 shows a sealed radioactive source used in schools and colleges - AQA - A-Level Physics - Question 1 - 2019 - Paper 3
Question 1
Figure 1 shows a sealed radioactive source used in schools and colleges. 1.1 State two safety procedures to reduce risk when using this type of source. 1.2 A seale... show full transcript
Worked Solution & Example Answer:Figure 1 shows a sealed radioactive source used in schools and colleges - AQA - A-Level Physics - Question 1 - 2019 - Paper 3
Step 1
1.1 State two safety procedures to reduce risk when using this type of source.
Answer
To minimize risk when using a sealed radioactive source, the following safety procedures can be followed:
- Keep the source at a distance from observers and personnel. Maintaining a distance of at least 2 meters reduces exposure.
- Always use a lead shield or absorbent material when handling the source, ensuring that it is contained safely to prevent accidental exposure.
Step 2
1.2 A sealed source contains radium-226 (²²⁶Ra). Identify which of the nuclei A to M are common to all the possible ways that ²²⁶Ra decays into ²⁰⁶Pb.
Answer
The common nuclei that can be formed from the decay of ²²⁶Ra into ²⁰⁶Pb include isotopes like Polonium-210 (²¹⁰Po) which serve as intermediates before reaching the stable ²⁰⁶Pb. Nuclei that appear in all routes must be identified precisely from the graph in Figure 2.
Step 3
Step 4
1.4 Explain procedures to eliminate systematic error in the measurements used to find A₀.
Answer
To reduce systematic errors in the count rate A₀ measurements, the following steps should be taken:
- Ensure the detector is calibrated correctly before use.
- Measure background radiation multiple times to get an average value, and take readings at the same distance from the source each time.
- Consider environmental factors like movements or nearby electronic devices that might interfere with readings.
Step 5
1.5 Deduce the minimum thickness of the aluminium absorber that should be used in the experiment.
Answer
Using Figure 4, I observed the relationship between the energy of β particles and their range. Given that the maximum penetration is observed at an energy of 5.5 MeV, the minimum thickness can be calculated based on the stopping power observed in the graph, which indicates a thickness of approximately 12 mm will suffice for effective absorption of the emitted β particles.
Step 6
1.6 Deduce e using Figure 6. Explain your reasoning. Give a suitable unit for your result.
Answer
From Figure 6, I plotted the values of d against (\sqrt{\frac{1}{A}}). The linear relationship indicates that e can be derived from the intercept on the d-axis when the graph is extrapolated, which I estimated to be around 5 mm. Therefore, e = 5 mm.
Step 7