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When you hear the horn of a car that is approaching you, thefrequency that you h

ID: 1748923 • Letter: W

Question

When you hear the horn of a car that is approaching you, thefrequency that you hear is larger than that heard by a person inthe car because
wave crests arefarther apart by the distance the car travels in oneperiod.
wave crests arecloser together by the distance the car travels in oneperiod.
the car getsahead of each wave crest before it emits the next one.
the speed ofsound in air is increased by the speed of the car.
a speeding caremits more wavecrests in each period. When you hear the horn of a car that is approaching you, thefrequency that you hear is larger than that heard by a person inthe car because wave crests arefarther apart by the distance the car travels in oneperiod. wave crests arecloser together by the distance the car travels in oneperiod. the car getsahead of each wave crest before it emits the next one. the speed ofsound in air is increased by the speed of the car. a speeding caremits more wavecrests in each period.

Explanation / Answer

The frequency f' that will be percieved by our stationaryobserver on the ground is given by f' = (Vsnd/') = (Vsnd/ * (1- Vsource/vsnd)) since (Vsnd/) = f,then f' = (f/(1 - Vsource/vsnd)) Because the denominator is less than 1,the observed frequencyf' is greater than the source frequency f.That is, f' > f.Therefore,wave crests are closer together by thedistance the car travels in one period.