alleryAn observer moves towards a stationary bell. What do they hear?
AA lower frequency than emitted
BExactly the frequency emitted
CA higher frequency than emitted
DNo sound from the bell at all
Answer & Solution
Correct answer: C. A higher frequency than emitted
1. The Doppler effect appears when either the source or the observer moves.
2. An observer moving towards the source meets the compressions more often.
3. So they receive them at a higher frequency, and therefore a shorter wavelength.
4. Moving away gives the opposite, a lower frequency and a longer wavelength.
_Source: OpenStax Physics (high school, CC BY 4.0), Ch 14 "Sound", section 14.3 Doppler Effect and Sonic Booms_
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