Physics (AS & A Level) · May / June 2025 · Paper 13 · Question 28

Electromagnetic waves of equal wavelengths are emitted from two sources, X and Y. The waves are emitted from X and Y with a phase difference of 180°. A detector moves along a path that is parallel to the line XY and detects a pattern of intensity maxima and minima. The diagram shows the arrangement of the sources and the path of the detector. An intensity maximum is detected at point Z. Length XZ is 70 cm and length YZ is 110 cm. What is a possible wavelength of the waves?

1. A10 cm
2. B16 cm
3. C20 cm
4. D40 cm

As printed in the paper