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Homework Help: Wave function

  1. Jul 1, 2009 #1
    1. The problem statement, all variables and given/known data

    im quite confused of describing whether these wave functions y(x,t)= sin(kx-wt) ; y(x,t)=sin(kx+wt) ; y(x,t)=cos(kx-wt) ; y(x,t)=cos(kx+wt) travel to the right or to the left.

    My prof told me that y(x,t)=sin(wt-kx) travels to the right (+x direction) but based on my other book, it's moving to the left (-x direction) pls can someone explain it to me? pls thank you...
  2. jcsd
  3. Jul 1, 2009 #2


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    Find out for yourself. Pick a fixed constant amplitude value on the wave, say c=sin(wt-kx) and see how it moves. The sin is constant if wt-kx is some constant, say b. So b=wt-kx. Now solve for x, so x=(wt-b)/k. I would say that means if t increases, then x increases (presuming w>0 and k>0). So I would say, 'right moving'.
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