Physics (AS & A Level) · Oct / Nov 2025 · Paper 13 · Question 28

A student carries out a double-slit experiment using a laser emitting red light of wavelength of 680 nm. The light is incident normally on a double slit. The diagram shows part of the pattern of bright fringes visible on a screen at a distance of 2.4 m from the slits. The distance across five bright fringes is measured as 34 mm. [diagram of fringe pattern with 34 mm across five fringes] What is the slit separation?

1. A8.5 × 10⁻³ m
2. B2.4 × 10⁻⁴ m
3. C1.9 × 10⁻⁴ m
4. D4.8 × 10⁻⁵ m

As printed in the paper