alleryStart learning →An observer moves away from a stationary source of sound. What do they receive?
AA higher frequency than emitted
BA lower frequency than emitted
CThe same frequency as emitted
DA frequency that keeps rising
Answer & Solution
Correct answer: B. A lower frequency than emitted
1. Moving away means each compression has further to travel than the one before.
2. They therefore arrive less often, which is a lower frequency.
3. A lower frequency corresponds to a longer wavelength.
4. Riding a train past a warning bell gives exactly this high-to-low shift.
_Source: OpenStax Physics (high school, CC BY 4.0), Ch 14 "Sound", section 14.3 Doppler Effect and Sonic Booms_
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