The optical properties of matter are based on the coupling of the incident electromagnetic radiation to oscillators within the material. The oscillators could be electrons, ions or molecules. Close to a resonance the dielectric function indicates strong dispersion and might be negative.
Electromagnetic radiation (EM), the disturbance in space that propagates by itself in the space has both electric and magnetic field components that oscillate in perpendicular to each other in phase and to the direction of energy. Spectrum scarcity is one of the