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Homework Help: What is the wavelength of the sound waves?

  1. Mar 20, 2010 #1
    1. The problem statement, all variables and given/known data
    a stationary sound wave has a series of nodes. The distance between the first and the sixth node is 30.0 cm. What is the wavelength of the sound waves?

    2. Relevant equations

    3. The attempt at a solution
    well no idea about it
    but in my attempt to solve it, i tried assuming 2L = [tex]\lambda[/tex]
    but there are 6 nodes so [tex]\lambda[/tex] = [tex]\frac{1}{3}[/tex]L
    by substituting the value of dist, i get [tex]\lambda[/tex] = 10cm
    which is wrong. the ans is 12.0 cm
    i wonder how to solve it
  2. jcsd
  3. Mar 20, 2010 #2
    Re: waves

    Try drawing yourself a diagram of the problem (ie just draw a wave going through six nodes), you should be able to solve it a bit more easily once you can visualise it.
  4. Mar 20, 2010 #3
    Re: waves

    Your current working is neglecting the fact that there are two nodes at either end of this hypothetical wave. (kind of analogous to a similar problem you are probably familiar with - ie if a farmer had 100m of wire to build a fence and he could place the posts 2m apart, how many posts would he need?)
  5. Mar 20, 2010 #4
    Re: waves

    i think i know it
    probably i should count the between one
    so it should be [tex]\frac{2}{5}[/tex] L = [tex]\lambda[/tex]
    by computing it
    i get 12.0 cm
    thx all of you
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