Optical Transmission and Refraction at the Atomic Level

The standard explanations for the phenomena of transmission and refraction of electromagnetic waves of optical wavelengths upon entering a transparent medium is in terms of the speed of the waves being altered. However, these phenomena are explicable without assuming that the speed of electromagnetic waves changes. The actual speed does not alter in various media but is customarily assumed to do so as this facilitates straight-forward calculations and allows easily understood explanations to be advanced. An underlying account of transmission and refraction at the level of individual atoms is presented in which the speed of electromagnetic waves remains constant.