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MCAT Physics Question — Sound Properties

A passing ambulance at first has a higher pitched siren while approaching a stationary observer followed by a lower pitch as it drives away. Which property of the sound changes as it passes?


a) speed of sound traveling in the medium

b) perceived frequency

c) actual frequency

d) there is no change to any property of the sound



The doppler effect manifests in a higher perceived frequency as a sound source approaches a detector and a lower perceived frequency as the source moves away from a detector.

doppler effect

a) speed of sound traveling in the medium, incorrect, The speed of sound does not change.

b) perceived frequency, correct.

c) actual frequency, incorrect, The actual frequency of the sound stays the same, while the perceived frequency is dependent on the velocity of the source relative to the detector.

d) there is no change to any property of the sound, incorrect, The perceived frequency changes per the doppler effect.

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