Physics (AS & A Level) · Feb / March 2018 · Paper 12 · Question 24

A vehicle carries a microwave transmitter that emits microwaves of a constant frequency. A stationary observer has a microwave receiver. The vehicle moves directly towards the observer at constant speed. The observer detects microwaves of frequency F₀. The vehicle then accelerates, still moving towards the observer, travels at higher steady speed for a time and then decelerates until it stops. What is the variation in the frequency of the microwaves that are detected by the observer?

1. AThe observed frequency will fall, then remain steady then return to the frequency F₀.
2. BThe observed frequency will fall, then remain steady then rise to a higher frequency than F₀.
3. CThe observed frequency will rise, then remain steady then fall to a lower frequency than F₀.
4. DThe observed frequency will rise, then remain steady then return to the frequency F₀.

As printed in the paper