Car A moves at speed v toward car B,which is at rest.The frequency of car A's horn is observed by car B to be f.What is the frequency of car A's horn as heard by an observer in car B if car A is at rest and car B moves at speed v toward car A (assume there is no wind)?
A)f
B)greater than f
C)less than f
D)either greater than or less than f
E)2f

Question

Quizplus · Accepted Answer

The Doppler effect causes the frequency of a wave to change when the source and observer are moving relative to each other. In this case, the source (car A's horn) is at rest and the observer (car B) is moving toward it. This means that the frequency of the wave will be lower than the original frequency.

Car a Moves at Speed V Toward Car B,which Is