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How do you define wave speed

  1. Sep 26, 2007 #1
    say for example there is a pulse through a string .then what exactly is wave speed or for that matter in case of unidirectional wave motion
     
  2. jcsd
  3. Sep 26, 2007 #2

    russ_watters

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    Could you rephrase the question....I'm not sure what you are asking. Are you asking what determines the speed of a wave? If so, the answer is the tension and elastic modulus of the string.
     
  4. Sep 27, 2007 #3
    how do u define wave speed
     
  5. Sep 27, 2007 #4

    ZapperZ

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    What's wrong with [itex]v=f\lambda[/itex]?

    Zz.
     
  6. Sep 27, 2007 #5
    i want to have the definition well the espression is well one perhaps a physical interpretation will do
     
  7. Sep 27, 2007 #6
    Well, you get a wave, and look at how fast the peaks and troughs are moving.
     
  8. Sep 27, 2007 #7

    ZapperZ

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    Could you say that again and maybe, this time, include a few punctuations?

    Zz.
     
  9. Sep 27, 2007 #8
    Sorry i didn't realize that how difficult is it to read that line without punctuation.
    Could u please define Wave speed in general mathematically
     
  10. Sep 27, 2007 #9

    f95toli

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    There is no general definition for the speed of a "wave" if you by "wave" also mean pulses etc.

    *The velocity at which a plane wave would propagate through a medium [tex]c[/tex] this is a constant which depends on properties of the medium (e.g. the speed of light or the speed of sound)

    *Phase velocity, [tex]v_p=\omega/\beta[/tex], is the speed at which a constant phase point (i.e. a maximum) travels. [tex]\beta[/tex] is the propagation constant.

    *Group velocity [tex]v_g=(d\beta/dt)^{-1}[/tex], is the speed at which a signal (such as a pulse) propagates thorugh a medium. This is only a meaninfull concept for signals with a narrow bandwidth or in media with low dispersion.

    Note that you can have [tex] v_p>c[/tex].
     
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