Attached Link: http://www.du.edu/~jcalvert/optics/plane.htm

Here's a link with more technical information on the subject. Everything absorbs light to some degree, therefor has an index of refraction. Even metal absorbs light (as well as reflects it). If it only reflected ALL light, you wouldn't be able to see it's topology at all with the human eye. It would just be a blinding white glow. ;-) Quote: "The fact that the colour of copper or gold remains shows that the light still does penetrate the metal enough to receive the colour (by absorption)."

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