CAPE Physics Unit 1 · 2008 · Paper 2 · Question 5(b)(ii)

The spectrum of sodium contains two yellow lines (Sodium D lines) close together with wavelengths of 589 nm and 590 nm, as shown in Figure 5. An experimenter uses a diffraction grating with 6 x 10⁵ lines per metre to view these lines separately.

What is the angular separation of the two sodium lines in this spectrum?

This question uses a figure or table from the paper — you'll see it when you practise.