Dielectric dispersion

Because polarization cannot follow an electric field in a high-frequency field, permittivity has a dependence on the frequency. This dependence is called dielectric dispersion. It is very important for the application of dielectric materials and the analysis of polarization systems.

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When the frequency becomes higher:

1. it becomes impossible for dipolar polarization to follow the electric field in the microwave region around 10¹⁰ Hz;
2. in the infrared or far-infrared region around 10¹³ Hz, ionic polarization loses the response to the electric field;
3. electronic polarization loses its response in the ultraviolet region around 10¹⁵ Hz.

In the wavelength region below ultraviolet, permittivity approaches the constant ε₀ in every substance, where ε₀ is the permittivity of the free space. Because permittivity indicates the strength of the relation between an electric field and polarization, if a polarization process loses its response, permittivity decreases.

See also

• Dielectric relaxation
• Dielectric spectroscopy