A-LevelPhysicsSuperposition9702/12 · Oct/Nov 2018 · Q301 Mark
A parallel beam of monochromatic light of wavelength λ is incident normally on a diffraction grating G. The angle between the directions of the two second-order diffracted beams at P₁ and at P₂ is α, as shown. [Figure 30.1] What is the spacing of the lines on the grating?
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A2λ / sin α
Bλ / sin α
C2λ / sin(α/2)
Dλ / sin(α/2)
✓ Correct answer
C: 2λ / sin(α/2)
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