Hypothesis on the Microscopic Mechanism of Light Interface Effects Based on Ether Density Gradient: A Unified Explanation of Reflection, Refraction and Evanescent

Aiming at the problems of traditional optical theories, including the vague physical picture of the interface mutation model, the half-wave loss relying on artificial boundary conditions, and the lack of intuitive explanation for the evanescent wave mechanism, this paper proposes a unified hypothesis on the microscopic mechanism of light interface effects based on the longitudinal-transverse composite wave ether model. The hypothesis holds that the ether density presents a continuous gradient distribution in space. On the atomic scale, there is a radial density gradient around the atomic nucleus, forming a high-density "energy shell". On the macroscopic scale, the ether inside the medium has a uniform average density, which determines the overall refractive index. The surface of the medium is not an abrupt interface, but a transition layer with continuously changing density. Inside a uniform medium, the periodic arrangement of atoms leads to destructive interference of scattered sub-waves, which macroscopically manifests as transparency and reduced speed of light. At the interface, the interruption of atomic arrangement makes backward scattering unable to cancel out, and superposes to form macroscopic reflected light. Based on this microscopic picture, this paper systematically explains the phenomena of reflection, refraction, total internal reflection, evanescent wave and half-wave loss at both light-optically thinner → optically denser and optically denser → optically thinner interfaces. All effects are naturally derived from the interaction between the ether density gradient and photons, without additional assumptions of boundary conditions. This paper also presents testable inferences and verification ideas of the model, providing a self-consistent classical hydrodynamic explanation framework for interface optical phenomena.