Sign of Wavenumber: Electromagnetic Material

[daudaudaudau]

Hi.

In electromagnetics, a material(linear,isotropic,homogenous) with constitutive parameters \epsilon and \mu has the wavenumber k^2=\omega^2\epsilon\mu. Consequently k=\pm\omega\sqrt{\epsilon\mu}. Does this mean that \omega 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.

 

[Antenna Guy]

Hi.

In electromagnetics, a material(linear,isotropic,homogenous) with constitutive parameters \epsilon and \mu has the wavenumber k^2=\omega^2\epsilon\mu. Consequently k=\pm\omega\sqrt{\epsilon\mu}. Does this mean that \omega 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.

k=\frac{2\pi}{\lambda}

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