Physics (AS & A Level) · Oct / Nov 2024 · Paper 13 · Question 29

A source of coherent light is incident on two slits, P and Q, which are placed 80 mm apart. The light has a single frequency of 1.5 × 10^12 Hz. The light from the slits meets on a screen that is a distance of 4.0 m from the slits. The screen is parallel to a line joining the slits. An intensity sensor is placed on the screen at the midpoint of the interference pattern such that the intensity reading is a maximum. The intensity sensor is moved along the screen. The sensor travels through two intensity minima, two intensity maxima and stops in the middle of the third intensity minimum. Which distance does the sensor move through?

1. A4.0 mm
2. B10 mm
3. C25 mm
4. D50 mm

As printed in the paper