Does light lose energy when it travels through a dense medium such as glass?

Question

Light slows down when it travels through glass but it speeds up again once it leaves the glass.  Doesn't the acceleration of light back to c, as it travels out of the glass, result in a loss of energy for the photon? If so, wouldn't the cumulative effects of light traveling through space (which is not empty) for billions of years result in a net loss of energy for a photon?

Sirnot Ett · Accepted Answer

Currently, science believes that the only way photons can lose energy is by passing through certain supercooled gases, which only a few experiments have been done to prove this. Otherwise, the speed of light is constant. It never slows or speeds up by passing through normal matter. This is obviously because the energy needed to try to go over the speed of light would become so great that it would soon come to infinity just to stay at 99.99999999999% the speed. Only space can move faster than the constant speed of light, and unlike other particles it does not slow down or lose part of itself by moving through a dense medium, even up to lead.

Does light lose energy when it travels through a dense medium such as glass?

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