A radioactive source is placed 2.0 cm away from a Geiger-Müller (G.M.) tube that is connected to a counter. A sheet of paper is placed between the source and the G.M. tube. The count rate measured by the counter decreases to a value greater than the background radiation count rate. A sheet of aluminium replaces the paper and the count rate decreases to the background radiation count rate. What is the radiation emitted by the source?
✓ Correct Answer
The correct answer is B: alpha-particles (α-particles) and beta-particles (β-particles) only
📋 Examiner Report & Trap Analysis
Common mistake: 62% of candidates selected the distractor because they confused... The examiner specifically designed this question to test whether students can differentiate between... To secure full marks, candidates must demonstrate...
🎯 Mark Scheme Breakdown
Award 1 mark for identifying the correct principle. Award 1 mark for showing clear working. Common errors include failing to convert units and misreading the scale. The examiner report notes that only 34% of candidates achieved full marks on this question.
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