a dimensionless complex scalar quantity n, characteristic of a medium at a given point and in a given direction, when there can exist in the medium a sinusoidal electromagnetic wave whose wave vector has colinear real and imaginary parts and , in the given direction; this quantity is defined by the equation:
where ω is the angular frequency, c0 is the velocity of propagation of electromagnetic waves in vacuum and is the unit vector in the given direction
NOTE 1 – For an isotropic medium, the complex refractive index is the square root of the product of the relative complex permittivity and the relative complex permeability.
NOTE 2 – For each direction in an anisotropic medium, there are generally two distinct wave vectors and two values of the complex refractive index.
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