ქიმიის ტერმინთა განმარტებითი ლექსიკონი

3 x 3 tensor that gives to first order the electric displacement, D, in a material in terms of the applied electric field, E, through D = ε_rε₀E, where ε₀ is the permittivity of vacuum.

Note 1: For isotropic materials the tensor is diagonal with the 3 diagonal elements equal, so a single quantity ε_r suffices.

Note 2: The equation D = ε_rε₀E is valid at all frequencies, and ε_r is a complex quantity, ε_r=ε`+iε”, where ε″ describes absorption. ε` is termed “real dielectric constant”, and ε” is termed “imaginary dielectric constant”

Note 3:  Relative permittivity is the square of the refractive index, thus

or, for a non-absorbing isotropic material, ε=n².