= Ohmic-conductor complex wavenumber
{title2=$k^2=\mu\epsilon\omega^2+i\mu\sigma\omega$}
With fields proportional to $e^{i(kz-\omega t)}$, a homogeneous Ohmic medium obeys the displayed relation by combining the two <curl> <Maxwell equations>. The physical passive branch has $\operatorname{Im}k\geq0$. For real positive conductivity much larger than $\omega\epsilon$, it reduces to $k=(1+i)/\delta$ with <skin depth> $\delta=\sqrt{2/(\mu\sigma\omega)}$. Field <amplitude> and <intensity> then decay with respective <lengths> $\delta$ and $\delta/2$. A frequency-dependent conductivity must be retained when charge-carrier inertia matters.
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