The Kramers-Kronig relations allows one to calculate the real part of the permitivity knowing the imaginary part or vice-versa:(adsbygoogle = window.adsbygoogle || []).push({});

http://en.wikipedia.org/wiki/Kramers-Kronig_relations

But in what situation will one know either the imginary part but not the real part or the real part but not the imaginary part of the permitivity?

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# Why are Kramers-Kroning relations useful?

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