Chapter 10.2, Problem 11R

To determine

To Draw:A diagram that explains Doppler Effect.

Explanation of Solution

Introduction:

The apparent change in the frequency of the wave when there is a relative velocity between the observer and the source is referred as Doppler shift/ Doppler effect.

The Doppler effect occurs because when the source move towards an observer, each crest of the wave is emitted from the position closer to the observer than the crest of the previous wave. As such, each wave takes lesser time to reach the observer than the previous wave. Hence, the time between the arrivals of each successive crest towards the observer is less. This increases the frequency. In this case, the distance between successive crests is reduced and the waves are bunched together as shown in figure 1.If the source is moving away from the observer, each wave moves a position farther from the observer, so the time of arrival between successive crest is increased, thus reducing the frequency. The distance in this case is increased and the waves will be spread out as shown in figure2.

  

  

Figure 1. Wavefronts bunched together Figure 2. Wavefronts spaced out

Conclusion:

Thus, any relative motion between source and the observer causes a Doppler Effect in the frequency.