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I Deriving equation of wave motion

  1. May 28, 2017 #1
    The equation below (2.9) is also a linear differential equation.
    This equation also describes the wave phenomena.
    So, why is this equation not considered as wave equation?
    I have taken it from the optics book by Chapter two Eugene Hecht,5th edition ,Pearson.
    upload_2017-5-28_17-56-55.png

    upload_2017-5-28_17-50-0.png upload_2017-5-28_17-50-39.png upload_2017-5-28_17-51-8.png upload_2017-5-28_17-51-45.png
    [​IMG]
     
    Last edited: May 28, 2017
  2. jcsd
  3. May 28, 2017 #2
    I must say that this is the worst derivation of the D'Alambert equation I've ever seen. It's simple but seems to describe any differentiable function. It is true that "wave" is a really general concept, in fact there are many different kind of waves and many different equation describing them, but it's not like anything is a wave!
    Anyway, as the text say on page 21, you need at least a second order differential equation to describe a wave since it has in the simplest case an amplitude and a frequency, so two parameters wich requires two conditions.
     
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