The oscillating electric field of the light wave induces a sympathetic oscillation of the electric charges bound to atoms or molecular bonds in the material. Th

The oscillating electric field of the light wave induces a sympathetic oscillation of the electric charges bound to atoms or molecular bonds in the material. The degree to which those charges can align themselves to the field is a characteristic of each material. Taking that polarizability into account in Maxwell's Equations yields a wave equation for electromagnetism, just like it does in a vacuum, but with a different propagation velocity, slower than the speed of light. In a vacuum, there's a corresponding polarizability of free space, related to the speed of light. In undergrad electrodynamics, prior to learning about relativity or quantum, we didn't try to explain it any further than that. It's transparent because the electrons stay attached to their atoms. If they could break free, then conduction would occur, and another solution of Maxwell's equations shows the wave being quenched. You could imagine conduction causing loss of energy via heating, like the way an electric stove works. If the electrons could absorb energy by making a quantum transition, some of energy could be released as heat rather than light. Refraction and reflections could be thought of as necessary consequences of continuity at an interface between materials of different composition. A number of things related to electric and magnetic field vectors have to remain the same at both sides of the boundary. This is akin to a conservation law, and requires introduction of a third wave at the boundary -- the reflected wave -- to make everything balance. Another way to look at refraction is via Huygen's Principle, where each point on a wave front is a source of a spherical wave front, and accounting for the different speeds in the two materials (e.g., air and glass) gives the law of refraction. And there's even yet another explanation which can be found by figuring out the path that the light takes, which results in a minimum for the time of travel. It's interesting that the law of refraction was worked out before electromagnetism was understood. I'm an industrial physicist, and this is hand-wavy, but I'm trying for an explanation that doesn't require equations.