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Finding Maxwell's Equation parameters problem

  1. Oct 17, 2014 #1
    1. The problem statement, all variables and given/known data
    6446493600_1413525970.jpg

    2. Relevant equations
    http://esclab.tw/wiki/images/math/0/a/2/0a24f9d68ba8fd1a1a8e6c6b36a00be3.png [Broken]

    3. The attempt at a solution
    9964508400_1413525970.jpg


    Hello
    As you see the answers of 19 and 20 problems we should try to find K or B(wave number) in wave equation.both of equations are in air space but we can't use K=(2*pi*f)/V ( F=frequency & 2*pi*f=omega , V= light velocity 3*10^8) for both of them.
    could you tell me why we can't use the K=(2*pi*f)/V for both of them in air space?does it have any condition & reason that we should check them before solve the problems?

    Any help appreciated
     
    Last edited by a moderator: May 7, 2017
  2. jcsd
  3. Oct 17, 2014 #2

    Simon Bridge

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    Both of what? Both problems?
    Where does that relation come from?
     
  4. Oct 17, 2014 #3
    Thank you dear simon for you replay
    My meaning is why in problem (6-19) should we use k=w/c but in problem(6-20) we should not?
    your meaning is K=w/c?
     
  5. Oct 17, 2014 #4

    Simon Bridge

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    I mean - what physical property of the wave does k represent.

    The second case is in a medium - what is different about EM waves travelling in a medium compared with a vacuum?
    hint: if you took k=w/c for the second case, you could not use c=3x10^8m/s.
     
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