Physics (AS & A Level) · May / June 2025 · Paper 12 · Question 24

A teacher removes the turntable from a microwave oven and places a bar of chocolate in the oven. She then switches the oven on for a short time. A stationary wave is formed in the oven. When the chocolate is removed, the teacher observes that there are two small sections of melted chocolate 6.0 cm apart with unmelted chocolate in between. Each section of melted chocolate is located at an antinode. [diagram showing a bar with two melted chocolate sections 6.0 cm apart] Assume that the speed of the microwaves is 3.0 × 10^8 m s^–1. What is the frequency of the microwaves emitted by the oven?

1. A25 MHz
2. B50 MHz
3. C2.5 GHz
4. D5.0 GHz

As printed in the paper