Physics (AS & A Level) · May / June 2026 · Paper 11 · Question 28

Water waves of wavelength λ are incident normally on an obstacle with a narrow gap. The width of the gap is equal to λ. The waves from the gap emerge over an angle θ as shown. The gap is slowly widened. Which changes, if any, occur to θ and to the wavelength of the emerging waves?

1. Aθ decreases, wavelength remains the same
2. Bθ increases, wavelength remains the same
3. Cθ remains the same, wavelength decreases
4. Dθ remains the same, wavelength increases

As printed in the paper