Transmission of light
– An ongoing repetitive process of scattering and re-scattering.
– The speed in which light travels in the medium is the overall rate of transfer of energy across some distance of medium. It depends on the phase difference between the scattered wave and the oncoming original wave. If the resultant wave lags the original, it will result in a decrease in speed.
Huygen’s principle states that every point on a wavefront can be regarded as a source of secondary spherical wavelets that spreads with the wave speed and the new wavefront is the envelop of these secondary wavelets.