When you hear the horn of a car that is approaching you, the frequency that you hear is larger than that heard by a person in the car because for the sound you hear
A) wave crests are farther apart by the distance the car travels in one period.
B) wave crests are closer together by the distance the car travels in one period.
C) the car gets ahead of each wave crest before it emits the next one.
D) the speed of sound in air is increased by the speed of the car.
E) a speeding car emits more wavecrests in each period.

Question

Quizplus · Accepted Answer

The frequency of the sound wave is determined by the number of wave crests that pass a given point per unit time. As the car approaches, the distance between wave crests (wavelength) decreases in the direction of the observer, thus increasing the frequency of the sound wave heard. This effect is known as the Doppler effect.

When You Hear the Horn of a Car That Is