Multiple choice

Doppler's effect is produced when the source and the observer are

  1. moving

  2. in relative motion

  3. stationary

  4. in space
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The Doppler effect is the change in frequency or wavelength of a wave in relation to an observer who is moving relative to the wave source. This effect occurs whenever there is relative motion between the source and the observer, causing the perceived pitch to rise as they approach and fall as they move apart. It is commonly heard when a siren passes by.

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