Physics (AS & A Level) · May / June 2020 · Paper 12 · Question 29

The diagram shows an arrangement for demonstrating two-source interference using coherent light of a single wavelength λ. An interference pattern is observed on a screen 3.0 m away from the slits X and Y, which have a separation of 1.0 mm. The central bright fringe is at Q, and the second bright fringe from the centre is at P. What is the distance between Q and P?

1. A6.0 × 10³ λ
2. B3.0 × 10³ λ
3. C6.7 × 10⁻⁴ λ
4. D3.3 × 10⁻⁴ λ

As printed in the paper