Question:medium
A train moving at 20 m/s approaches a stationary observer. The frequency of the whistle emitted by the train is 640 Hz. If the velocity of sound is 340 m/s, the apparent frequency heard by the observer is:
A train moving at 20 m/s approaches a stationary observer. The frequency of the whistle emitted by the train is 640 Hz. If the velocity of sound is 340 m/s, the apparent frequency heard by the observer is:
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Source moving towards observer $\Rightarrow$ use minus in denominator ($v - v_s$) $\Rightarrow$ frequency increases. Source moving away $\Rightarrow$ plus in denominator $\Rightarrow$ frequency decreases.
Updated On: May 16, 2026
- 680 Hz
- 600 Hz
- 720 Hz
- 640 Hz
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The Correct Option is A
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