Physics (AS & A Level) · May / June 2026 · Paper 13 · Question 30

A microwave source is placed on a horizontal surface at position X. A shiny metal sheet is placed at position Y that is a distance of 0.48 m from X. [diagram: microwave source, microwave detector, metal sheet, 0.48 m, X, Y] The microwaves are reflected back from the metal sheet towards the source. A microwave detector is moved from X to Y and all positions of minimum microwave intensity are recorded. Intensity minima were detected at X and Y and also at 15 positions in between X and Y. The speed of the microwaves is 3.0 × 10⁸ m s⁻¹. What is the frequency of the microwaves emitted by the source?

1. A4.7 × 10⁹ Hz
2. B5.0 × 10⁹ Hz
3. C9.4 × 10⁹ Hz
4. D1.0 × 10¹⁰ Hz

As printed in the paper