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Summary

These equations, together with the definitions 4.15 and 4.20, are regarded as the basie

laws of electrodynamics in the presence of media. Notę that they are quite generał in that

they do not assume linearity or spatial uniformity of those media.

Because these equations have introduced additional variables, they no longer contain sufficient information for the solution to practical problems. Before a solution to a practical

problem can be obtained we need additional information. Such additional information

comes from specifying the relation between E and P (or E and D) and between H and M(or H and B) within these media.

The specification of E-P andH-Mrelations for various classes of media is the subject of the nextchapter.