Practice IB Physics Topic C.5 Doppler Effect with authentic exam-style questions for both SL and HL students. This question bank focuses on the exact syllabus content for C.5 Doppler Effect and mirrors Paper 1A, 1B, 2 style where relevant.
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A spacecraft, while receding from Earth at , emits light at a rest frequency of . An Earth-based observer detects a redshifted signal. The frequency received on Earth is approximately .
Determine the wavelength of the light as measured in the rest frame of the spacecraft.
Determine the observed wavelength of the light on Earth.
Explain why the observed frequency on Earth is lower than the emitted frequency, even though the light travels at the same speed in all frames.
The diagram shows a stationary observer while a loudspeaker moves toward them, emitting a constant sound. The observer hears a change in the pitch of the sound due to the relative motion of the source.
State what happens to the frequency of the sound as heard by the observer.
Outline why this change in frequency occurs.
Suggest what would be heard if the source were moving away from the observer instead.
Describe one real-life situation in which this Doppler effect can be experienced.
A loudspeaker moves to the left at speed , where is the speed of sound in air. It emits sound of frequency . A stationary observer is in front of the loudspeaker.
Which of the following gives the observed frequency heard by the observer?
A fire truck moves past an observer at constant speed. Why is the siren pitch higher as it approaches than as it recedes?
A high-speed train travels at a constant velocity toward a station platform where a stationary observer is standing. The train's whistle emits a sound of a constant frequency.
In the context of the moving train, explain why the observer detects a shorter wavelength than the one emitted by the whistle.
The following data were recorded for the sound produced by the train as it approached the station:
| Variable | Value |
|---|---|
| Frequency of whistle () | |
| Frequency detected by observer () | |
| Speed of sound in air () |
Calculate the speed of the train, .
Describe the change in the frequency detected by the observer at the instant the train passes them and begins to move away.