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Homework Help: Standing waves and maximum intensity?

  1. Jun 14, 2009 #1
    1. The problem statement, all variables and given/known data
    "Two loudspeakers emit sound waves along the x-axis. The sound has maximum intensity when the speakers are 27.5 cm apart. The sound intensity decreases as the distance between the speakers is increased, reaching zero at a separation of 60.5 cm. What is the wavelength of the sound?"

    I think this is more of a conceptual question that doesn't involve any actual calculation? I think it just involves an understanding of wavelengths and standing waves

    2. Relevant equations

    3. The attempt at a solution
    I tried to work this one out, and this would be my reasoning, but it obviously doesn't fit in with the numbers given...
    with my assumptions, I *should* be getting 1/2 wavelength = 27.5cm, and 1 wavelength = 55cm

    So to work out this problem, I drew two sets of diagrams.
    (1) The first diagram has speakers that are 27.5cm apart. Since this is when max intensity is generated, I figured that the antinode must be made in the middle, and that the waves shouldn't cancel out, and instead should be constructively superimposed - ie. added together without cancelling out. So in my diagram, the waves generated in this case make 1/2 a wavelength, which is 27.5cm.

    (2) In the second diagram, Since this would be when intensity is zero, I thought that the two waves must cancel out... but still, this doesn't fit in with the assumption that the first case represents 1/2 wavelenght, and the second case represents a full wavelength
  2. jcsd
  3. Jun 15, 2009 #2
    I would guess that you need to consider the situation slightly differently.

    assuming you had the speakers set up to produce a standing wave, then moved one of them further away by one full wavelength, what would happen? what would happen as you moved the speaker?
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