Describe the properties of a wave based on the relative motion between the source of the wave and the observer of the wave.

• The Doppler effect describes the relationship between the rest frequency of a wave source, the observed frequency of the source, and the relative velocity of the source and the observer.
• A greater relative velocity results in a greater measured difference between the observed and rest frequencies.
• For a wave source moving at the same velocity as the observer, the observed frequency is equal to the rest frequency.
• For a wave source moving toward an observer, the observed frequency is greater than the rest frequency.
• For a wave source moving away from an observer, the observed frequency is less than the rest frequency.

Only qualitative treatments of the Doppler effect are required for AP Physics 2.

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