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Homework Help: Spherical Wave - What is the phase?

  1. Nov 1, 2007 #1
    1. The problem statement, all variables and given/known data

    A spherical wave with a wavelength of 2.0 m is emitted from the origin. At one instant of time, the phase at r=4.0m is pi radians. At that instant, what is the phase at r=3.5m?

    2. Relevant equations

    D(x,y,z,t)=Asin(kr-wt+phi)
    k=(2pi)/(lambda)
    w=(2pi)/T

    3. The attempt at a solution

    (kr-wt+(phi))=phase constant
    D(x,y,z)=displacement, or here, radius
    A cancels and doesn't matter.
    4/(pi)=3.5/x
    x=3.5(pi)/4 <---- which is wrong.

    So then I tried subtracting the equations...
    4=Asin(pi)
    -3.5=-Asinx
    .5=Asin(pi)-Asinx
    .5=Asinx <---- Then I didn't know what to do with it. Help please?
     
    Last edited: Nov 1, 2007
  2. jcsd
  3. Nov 1, 2007 #2
    Nevermind . . .
     
  4. Feb 19, 2008 #3
    I'd sure like to know.
     
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