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Physics (AS & A Level) · May / June 2021 · Paper 12 · Question 23

9702Progressive waves

A sound wave is detected by a microphone that is connected to a cathode-ray oscilloscope (CRO). The screen of the CRO displays a waveform, as shown. [waveform on CRO screen] The time-base is set to 20 µs div⁻¹. What is the frequency of the sound wave?

  1. A15 Hz
  2. B15 000 Hz
  3. C20 000 Hz
  4. D30 000 Hz

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Correct answer: B. 15 000 Hz

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