<P> Such coatings can reduce the reflection for ordinary glass from about 4 % per surface to around 2 % . These were the first type of antireflection coating known , having been discovered by Lord Rayleigh in 1886 . He found that old , slightly tarnished pieces of glass transmitted more light than new , clean pieces due to this effect . </P>
the amount of light reflected from the front surface of common window glass is about
about 4 % per surface