Glass, Brightness, and Reflectance
Name: Joshua T.
Hello. I hope I am not wasting your time on this
question, but I cannot seem to locate an answer. I believe I once
read, in reference to how light is reflected off of glass, and
dependant on the 'brightness' or 'darkness' on the other side, that
the amount of reflection happens in 8% increments. i.e. 8% is
reflected, then 16%, but not a number in between. Did I imagine
reading this? If not, was it explaining something else and I
misunderstood? Thanks a 1,000,000 for your help!
You are probably referring to the reflection of an air/glass
interface. The precise amount of light reflected at an air to glass
interface depends on the index of refraction of the glass but for "normal"
glass it is about 4%. There is an air to glass interface on
both sides of a piece of glass. 4% of the light entering the glass is
reflected and 96% transmitted. When it reaches the glass to air interface
an additional 4% of the 96% is reflected. Thus, of the light shining into
a window about 8% gets reflected back to the source side of the glass.
Hope this helps.
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Update: June 2012