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Sign of the wavenumber

  1. Sep 5, 2008 #1
    Hi.

    In electromagnetics, a material(linear,isotropic,homogenous) with constitutive parameters [tex]\epsilon[/tex] and [tex]\mu[/tex] has the wavenumber [tex]k^2=\omega^2\epsilon\mu[/tex]. Consequently [tex]k=\pm\omega\sqrt{\epsilon\mu}[/tex]. Does this mean that [tex]\omega[/tex] can actually be negative, and if so, when is it the case? It seems strange to me, but some guy told me today that a negative wavenumber was indeed possible.
     
  2. jcsd
  3. Sep 6, 2008 #2
    [tex]k=\frac{2\pi}{\lambda}[/tex]

    Negative k accounts for the opposite direction. As a wave approaches you, it is also moving away at the same rate (expanding spherically about the source).

    Regards,

    Bill
     
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