The difference between using Acos(wt-kz) travelling wave equation, and Acos(kz-wt)?

  • Thread starter km707
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  • #1
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We were taught in the vibrations and waves lecture course that the solution to the wave equation for traveling waves is of the form ψ(z,t) = Acos(wt-kz).
In the Electromagnestism course we learnt that EM waves are traveling waves and have the solution E = E0cos(kz-wt).

I know that changing the sign of the z term determines the direction of propagation along the z axis, but does that mean that the "-wt" term correspond to moving back in time? Or does the sign of the wt term not matter?

Thanks!
 

Answers and Replies

  • #2
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for the cosine function,
cos(kz-wt)= cos(wt-kz)

so it equals the a change of direction in space z.

does it answer you question?
 
  • #3
Vanadium 50
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I don't understand what enricferni is saying.

cos(x) = cos(-x), right?

So cos(wt-kz) = cos(kz - wt). They mean exactly the same thing.
 

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