Term:

Permittivity

Definition:

A quantity measuring the ability of a material to store electric energy in the presence of an electric field. It is denoted by the symbol .

Explanation:

In an isotropic, homogeneous, linear medium, the Electric “Displacement” D (analogous to current) is obtained as a product of the permittivity and the Electric Field intensity E (analogous to voltage): D = E In this way, permittivity is analogous to conductivity in a resistor. Sometimes is replaced by _{0 r}, where ₀ is the permittivity of free space, and _r is the relative permittivity or “dielectric constant” of the medium. The permittivity of free space is a constant equal to ₀ = 8.8542 x 10^-12 farads/meter.

Materials (surfaces) that have larger dielectric constants (e.g. wet soil vs. dry soil) means that a radar signal induces more (surface) current in them, which increases the strength of the scattered wave.

Related Terms:

Dielectric Constant
Permeability
Conductivity