Dielectric dispersion


Dielectric dispersion

In physics, dielectric dispersion is the dependence of the permittivity of a dielectric material on the frequency of an applied electric field. Because there is always a lag between changes in polarization and changes in an electric field, the permittivity of the dielectric is a complicated, complex-valued function of frequency of the electric field. It is very important for the application of dielectric materials and the analysis of polarization systems.

This is one instance of a general phenomenon known as material dispersion: a frequency-dependent response of a medium for wave propagation.

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

In the wavelength region below ultraviolet, permittivity approaches the constant "ε"0 in every substance, where "ε"0 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

* Dispersion (optics)
* Dielectric relaxation
* Dielectric spectroscopy

References


Classical Electrodynamics,John David Jackson Published by Wiley,1998 ISBN7130932X,780471309321


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