Maxwell’s identity

At optical frequencies, when only electronic polarization occurs, the dielectric constant is related to the refractive index by Maxwell s identity. A comparison between e values at different frequencies may assure a basic understanding of the influence of the molecular structure on the dielectric properties of Epiclon-based Pis. 

Figure 3. Dielectric constant dependence on frequency for Epiclon-derived Pis. The e values at 1 kHz, 10 kHz and 100 kHz were experimentally obtained on a LCR METER, while those at 1 MHz were estimated by Maxwell s identity using ellipsometrical measurements...

The main property of exact total differentials is that they obey Maxwell s identity, which is written ... 

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