From Microphysics to Mesophysics: Obtaining Effective Properties from Microscopic Behaviors
A. I. Căbuz · 2017
The reason why science took so long to realize that matter is grainy, and why only sufficiently advanced experimental techniques were able to determine that it is so, is that previously humans only observed matter on a large scale compared to the graininess. In an electromagnetic material, three scales determine its behavior: the wavelength of the harmonic field, the scale on which the medium is structured, and the distance over which the charges are free to move within the structure. Dielectric media are linear systems when the field intensity is not too large. As with any linear system, there are a number of degrees of freedom, some of which are of interest and some of which are either not of interest or in any case inaccessible or unobservable. According to the hydrodynamic model, one assumes that the medium under study supports two types of waves: the standard divergence-free transverse electromagnetic waves, plus the longitudinal plasma waves.