Negative Refraction as a Source of Some Pedagogical Problems

The appearance of material with negative values of dielectric and magnetic permeabilities ε and μ and with negative index of refraction n forces to revise the accustomed forms of some well-known formulae of electrodynamics. This is connected with fact, that these correlations in repressing majority of sources is written in tacit suggestion that magnetic permeability of most of materials is μ=1, factor of refraction n=ε and is undoubtedly executed the correlation n > 0. Such approach could be named as "nonmagnetic". However, if n <0, this nonmagnetic approach can bring very hard mistakes.