A-LevelPhysicsSuperpositionMay/June 2023Paper 1 Q281 Mark
The diagram shows a view from above of a double-slit interference demonstration. L is a monochromatic light source with a vertical filament. B is a barrier with two narrow vertical slits and S is a screen upon which interference fringes form. [Figure 28.1] The intensity is I at the point on the screen where the centre of the fringe pattern forms. When one of the slits is covered, what is the intensity at the same point on the screen?
AI/√2
BI/2
CI/(2√2)
DI/4
✓ Correct Answer
The correct answer is D: I/4
📋 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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