Negative Refraction in Plasma and Magnetic Materials

The possibility of negative refractive index in plasma and magnetic materials was considered with a new approach. It is shown that simplification of fundamental equations by neglecting losses leads to losing important features about refractive index and therefore, it is expedient to take into consideration imaginary parts of dielectric permittivity and magnetic permeability for an accurate statement of the problem. Also active materials were briefly discussed via new approach.