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1 markProperties of Waves

CAPE Physics Unit 1 · 2010 · Paper 2 · Question 5(b)(ii)

Figure 7 shows a loudspeaker connected to an audio-frequency signal generator/amplifier set up in front of a large flat wall. A small microphone detects regions of low and high intensity between the speaker and the wall.

The points labelled X on Figure 7 are the only three points of minimum intensity detected at a certain frequency setting. What is the frequency?

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Other parts of this question

  1. 5(a)(i)Explain what is meant by 'threshold of hearing' and 'threshold of pain'.[1 mark]
  2. 5(a)(ii)What property of the human ear makes the decibel (dB) scale particularly useful?[1 mark]
  3. 5(a)(iii)Write down an expression that relates the sound intensity I, to the intensity level β, in dB.[1 mark]
  4. 5(a)(iv)What is the intensity level of a sound with intensity 3.82 mW m⁻²?[1 mark]
  5. 5(a)(v)Figure 6 is drawn for a typical human ear. Suggest how the figure might change as a person ages.[7 marks]
  6. 5(b)(i)Explain why there are positions between the speaker and the wall where intensity is a minimum and why these minima do NOT actually have zero intensity.[1 mark]
  7. 5(b)(iii)When the signal generator is set at 165 Hz how far from the wall is the last maximum intensity position? [Velocity of sound = 330 m s⁻¹][8 marks]

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