A Monochromatic source of light in a vaccuum shines light into a block of glass. How does the amplitude of the light wave change once it is inside the glass and once it leaves the glass. I know that some energy (and hence amplitude) is lost by the light wave when it enters the glass due to slight reflection. But is that quantity of energy even measurable? Since I am only interested in the theoretical aspect of this problem, would that mean that the energy and amplitude of the wave are assumed to remain constant throughout? If not, how do they decrease once inside the glass?