Green through the glass

These are two views of a glass television table. It was about 2cm thick and 75cm long. The top picture is looking down through the glass. You can hardly see it. There is a green strip along the top of the lower photograph. That is looking endways on into the glass. Glass contains some iron impurities. The iron ions absorb at the red and the blue ends of the spectrum so only the green gets through. It happens along the length because a lot of ions are needed to make the effect noticeable.