Physics (AS & A Level) · Oct / Nov 2021 · Paper 12 · Question 30

Light of wavelength 5.5 × 10⁻⁷ m is incident normally on a diffraction grating. The angle between the second-order diffraction maxima is 80°, as shown. What is the number of lines per metre of the diffraction grating?

1. A5.8 × 10⁵ lines per metre
2. B9.0 × 10⁵ lines per metre
3. C1.2 × 10⁶ lines per metre
4. D2.3 × 10⁶ lines per metre

As printed in the paper