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Homework Help: Waves and Phase difference

  1. May 16, 2007 #1
    1. The problem statement, all variables and given/known data

    first of all, when two waves are out of phase. We tend to ay one wave lags by the other wave of x degrees. So what does lag mean. does it mean its displacement is less or more and how do i calculate the value of x.

    and does x also mean the phase difference between the two waves?

    so if x is o degrees both waves are coherent? yes or no
    and then in that case they superpose to form wave of resultand displacement due to both of the waves
  2. jcsd
  3. May 16, 2007 #2
    Well, when one is out of phase from the other you would say that it either lags or leads the other wave by some amount.

    For example, sin(x) leads cos(x), or you could say that cos(x) lags sin(x).

    Usually a phase lag is indicated by some other notation like Ø (phi). Given that you have two waves, cos(x+Ø) and cos(x). The term of cos(x+Ø) lags the term cos(x) by an amount of Ø. Cosine lags sine by π/2. cos(x-Ø) leads cos(x).

    I don't really know what you are asking about in your last question. The superposition of two waves happens often, and leads into the area of wave packets, group velocity, and other such concepts.
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