A siren emitting 400 Hz moves at 170 m/s directly towards a stationary listener. Taking the speed of sound as 340 m/s, what frequency does the listener hear?
Answer and explanation
Correct answer: D. 800 Hz
- Step 1: For a source approaching a stationary observer, .
- Step 2: Hz.
Answer
800 Hz.
Why not the others: 266.7 Hz: it uses the formula for a receding source. 570 Hz: the speed of the source is added to the frequency. 200 Hz: the ratio is inverted.
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