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12 marksProperties of Waves

CAPE Physics Unit 1 · 2005 · Paper 2 · Question 7(b)(v)

Two loudspeakers connected in parallel to a signal generator are used to demonstrate the interference of sound waves, analogous to light. Figure VI illustrates the setup. As a microphone moves along line YX, it detects a maximum of sound intensity at O and then another maximum at X. Velocity of sound in air = 330 ms⁻¹.

The phase of speaker P is changed by 180°. What effect will this have on the sound heard at points O and X ?

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Other parts of this question

  1. 7(a)(i)Derive the formula y = λD/a for interference of light waves from a double slit where y is the spacing of the fringes on a screen at a distance D from a double…[1 mark]
  2. 7(a)(ii)Explain why the formula gives only an approximate value.[8 marks]
  3. 7(b)(i)Find the distances PX and QX from the speakers to the first maximum at X and hence find the wavelength of the sound waves.[1 mark]
  4. 7(b)(ii)What value does the formula y = λD/a give for the wavelength of the sound waves?[1 mark]
  5. 7(b)(iii)Discuss the fact that the values given in (b) (i) and (ii) are different.[1 mark]
  6. 7(b)(iv)What is the frequency of the sound from the speakers?[1 mark]

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