- Dielectric dispersion
In physics, dielectric dispersion is the dependence of the
permittivityof a dielectricmaterial on the frequency of an applied electric field. Because there is always a lag between changes in polarizationand changes in an electric field, the permittivityof the dielectric is a complicated, complex-valued function of frequency of the electric field. It is very important for the application of dielectricmaterials 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
microwaveregion around 1010 Hz;
# in the
infraredor 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.
Classical Electrodynamics,John David Jackson Published by Wiley,1998 ISBN7130932X,780471309321
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