Skin depth
= Skin depth
{title2=$\delta$}
The <skin depth> is the distance over which a field amplitude falls by $e^{-1}$ inside a conductor. In the local good-conductor limit, $\delta=\sqrt{2/(\mu\sigma\omega)}$. Intensity then falls by $e^{-2}$ over one <skin depth>; amplitude and intensity penetration lengths differ by a factor two.