The abstract theory posits that light propagation in a medium is governed by the phase velocity ($v_p$), which arises from the superposition of incident electromagnetic waves and induced oscillations of bound charges modeled as harmonic oscillators. The index of refraction ($n = c/v_p$) is determined by the resonant response frequencies of these charge distributions, where $n < 1$ occurs when the optical frequency exceeds the material's resonance frequency, indicating that phase velocity can exceed $c$ without violating causality or allowing superluminal information transfer. This framework integrates classical electrodynamics with dispersive media theory to explain refraction mechanisms and phenomena such as birefringence and optical rotation within the domain of wave optics.
The abstract theory posits that light propagation in a medium is governed by the phase velocity ($v_p$), which arises from the superposition of incident electromagnetic waves and induced oscillations…