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Homework Help: Standing waves

  1. Jun 14, 2009 #1
    1. The problem statement, all variables and given/known data
    What is the longest wavelength for standing waves on a 254.0 cm long string that is fixed at both ends?

    2. Relevant equations

    3. The attempt at a solution
    When x = L (length of string):

    k(n) = n*pi / L
    wavelength (n) = n*pi / k(n)

    I got the answer, I just don't understand why these equations are used in my textbook to find this particular answer.
    Last edited: Jun 14, 2009
  2. jcsd
  3. Jun 14, 2009 #2


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    "how can a wave be made?"

    Imagine pulling on the rope hard, to make it taut. You could then make the rope vibrate like a guitar string.

    A wave has to be set up in the rope to make it vibrate. Obviously, the fixed ends can't be vibrating, which sets restrictions on the permitted wavelengths. So: what's the longest possible wavelength?
  4. Jun 14, 2009 #3


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