Optical properties of a three-dimensional composite medium consisting of an amplifying
matrix with inclusion of silver nanoparticles of various shapes are investigated theoretically.
Behaviour of the amplification coefficient of active component required for compensating
energy dissipation at metal inclusions is studied. Results of exact electrodynamical
calculations of conditions for obtaining the unit refractive index and that performed using
electrostatic approximation (Maxwell–Garnett approach) are compared.