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Homework Help: Equation of a wave pulse

  1. May 29, 2006 #1
    1)Is it true that y = a sin(wt) is the equation of a wave pulse and y = a sin(wt – kx) is the equation of a progressive wave?
    I think it is true.
    2)Will the following 2 waves produce stationary waves?
    y1 = a cos(kx – wt)
    y2 = a sin(kx + wt)
    I think the answer is No. What do you say Sir?
  2. jcsd
  3. May 29, 2006 #2
    [itex]y(0,t)=a\sin(\omega t)[/itex] is the wave as seen from [itex]x=0[/itex]. If you were to measure the vertical displacement [itex]y(0,t)[/itex] then you would find it to vary simple harmonically.

    A wave exists for all x and t whereas a pulse is a portion of a wave which exists for some time, much like the wave pulse generated when you shake one end of a string (the other end being fixed) before it strikes the end and standing waves are set up. To describe a pulse, you need to describe the wavefunction as [itex]y(x,t)[/itex] for some region when it is "on" and zero elsewhere. So you need to include the span of the wave pulse.

    Why don't you add the waves and see for yourself?? Its not that difficult and the best way to figure out is to add them yourself rather than have someone tell you the answer. :smile:
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