A-LevelPhysicsSuperpositionMay/June 2020Paper 1 Q301 Mark
Light of wavelength λ is incident normally on a diffraction grating. The angle between the second-order maximum and the normal to the grating is θ. The variation with sin θ of λ is shown on the graph. [Figure 30.1] How many lines per millimetre are on the diffraction grating?
A400 mm⁻¹
B625 mm⁻¹
C800 mm⁻¹
D1250 mm⁻¹
✓ Correct Answer
The correct answer is A: 400 mm⁻¹
📋 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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