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In deriving a complex wave vector for waves in media, an equationD= εEis typically used. Later though, it is common to relateDandEthrough a complex ε which is generally written as εcomplex = ε + 4 pi i σ / ω.

It seems a contradiction to insert one relationship into the Maxwell equations and then explain how really it's another, where a complex epsilon allows for a phase shift betweenDandE.

I'm also confused whether the σ here is necessarily complex; in the constituitive relation used to derive it, we hadj= σEand from the Dressel Electrodynamics of Solids book and the Wooten online optical solid state book he identifies σ as real.

See, for example, http://web.mit.edu/course/6/6.732/www/6.732-pt2.pdf pages 2-3.

Thanks!

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# Which dielectric constant in media?

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