Physics (AS & A Level) · May / June 2024 · Paper 11 · Question 27
9702Doppler effect for sound waves
The siren of a moving police car emits a sound wave with a frequency of 440 Hz. A stationary observer hears sound of frequency 494 Hz. The speed of sound in the air is 340 m s⁻¹. What could be the speed and the direction of movement of the car?
- A37 m s⁻¹ directly away from the observer
- B37 m s⁻¹ directly towards the observer
- C42 m s⁻¹ directly away from the observer
- D42 m s⁻¹ directly towards the observer
As printed in the paper
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Correct answer: B. 37 m s⁻¹ directly towards the observer
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