When I view most glass from the side it's green which I've found out is due to impurities in the glass specifically from iron oxide. Why is it when I view the larger face from an oblique angle, it isn't nearly as green?
I cannot personally notice any different on the piece I have next to me even when I hold it at an angle that would be almost looking at the edge of the glass. It is pretty small (about 2.5" x 5" x .0625" or about 61mm x 127mm x 2mm, l x w x h) but I feel like it's big enough that I'd be looking through enough glass to get the green.
Answer
As you stated, the degree of green is directly dependent on the thickness of glass you stare at (Beer-Lambert law). It actually comes from the absorption of the other wavelengths by the glass.
Due to refraction, even when you look at the glass from a grazing angle in the air, the light rays bend to a higher angle in the glass which makes the light path through the glass shorter (figure 2).
On the contrary, when you stare at the glass from the edge, total internal reflection makes the light rays travel through the whole length of the glass to your eye (figure 3).
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