Name: Bruce H.
Refraction of light is mainly due to difference in
permittivity. Classical theory of dielectrics attributes this to
polarisation in which the charge distribution of the atoms is affected by
the electric field.
I do not understand how changes in charge distribution can take place
within an atom at the rates corresponding to the frequency of light.
Perhaps it will help to consider that molecular vibrations produce
infrared radiation (frequencies in to 200 THz range and even
higher). This is related to the vibration (movement) of
nuclei. Electrons are several orders of magnitude less massive than nuclei.