Two identical loudspeakers are connected in series to an a.c. supply, as shown. [Figure 28.1] A microphone is moved along the line PQ. Which graph best shows the variation with distance from P of the intensity of the sound detected by the microphone?
✓ Correct Answer
The correct answer is A: [Graph A: intensity vs distance, showing constructive and destructive interference, starting with high intensity at P and gradually decreasing overall amplitude]
📋 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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