Doppler effect for sound waves: past paper questions

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• Question 24May/June 2026, paper 11Multiple choice1 markHas a diagram

  A train is travelling with a constant velocity. It operates its whistle as it moves directly towards a student. The whistle emits a continuous sound of constant frequency.

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• Question 27Oct/Nov 2025, paper 11Multiple choice1 mark

  A dolphin is swimming at a speed of $16.0{\text{ ms}}^{-1}$ directly towards a stationary underwater microphone. The dolphin emits a sound of frequency $122\text{ kHz}$. The speed of sound in water is $1480{\text{ m s}}^{-1}$.

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• Question 26Oct/Nov 2024, paper 12Multiple choice1 markHas a diagram

  A source of sound emits waves of a constant frequency. The source moves at a constant speed in a straight line relative to a stationary observer. Which velocity of the source gives the smallest observed frequency?

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• Question 22Oct/Nov 2023, paper 11Multiple choice1 markHas a diagram

  A toy drone emits a sound of constant frequency $800\text{ Hz}$. The speed of the sound in the air is $330{\text{ m s}}^{-1}$. The drone moves along a straight path directly towards an observer and then continues in a straight line directly away from the observer.

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• Question 24May/June 2026, paper 12Multiple choice1 mark

  The siren on an emergency vehicle emits a sound of constant frequency $1100\text{ Hz}$. The driver in a stationary car hears the sound at a frequency of $1000\text{ Hz}$. The speed of sound in air is $340{\text{ m s}}^{-1}$.

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• Question 24May/June 2026, paper 13Multiple choice1 markHas a diagram

  A loudspeaker moves with a constant speed relative to a stationary observer. The loudspeaker emits a sound of constant frequency. The frequency of sound observed depends on the speed and the direction of motion of the loudspeaker.

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• Question 24May/June 2025, paper 11Multiple choice1 markHas a diagram

  An aircraft produces a sound at a frequency of $30.0\text{ Hz}$. The speed of sound in air is $330\text{ m}{\text{ s}}^{-1}$. The aircraft is directly in front of the stationary observer and travels in a straight line towards or away from the observer.

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• Question 5Oct/Nov 2024, paper 23Structured8 marksHas a diagram

  A stationary wave is formed on a string XY that has a length of $0.48\text{ m}$. Fig. 5.1 shows the string at one instant in time. Fig. 5.1 The speed of the wave on the string is $1400{\text{ ms}}^{-1}$.

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• Question 27May/June 2024, paper 11Multiple choice1 mark

  The siren of a moving police car emits a sound wave with a frequency of $440\text{ Hz}$.

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• Question 5Oct/Nov 2023, paper 21Structured4 marksHas a diagram

  A train travels at a constant high speed along a straight horizontal track towards an observer standing adjacent to the track, as shown in Fig. 5.1.

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• Question 5May/June 2025, paper 21Structured6 marksHas a diagram

  Use the definitions of speed $v$, frequency $f$ and wavelength $\lambda$ to derive the wave equation $$v=f\lambda \text{.}$$

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• Question 24May/June 2024, paper 13Multiple choice1 mark

  An ambulance siren emits a sound with a single frequency $f$. The ambulance travels towards, passes close to, and then travels away from a stationary observer. Which statement describes the frequency of the sound detected by the observer as the ambulance passes the observer?

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