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