Physics (AS & A Level) · May / June 2020 · Paper 12 · Question 30

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. How many lines per millimetre are on the diffraction grating?

1. A400 mm⁻¹
2. B625 mm⁻¹
3. C800 mm⁻¹
4. D1250 mm⁻¹

As printed in the paper