Long description

A top-down photograph showing light refracting through a glass block. A beam of white light shines from left to right through a rectangular-shaped block of glass. Where the ray of light meets the glass, it is refracted upwards. Where the ray of light leaves the glass, it is refracted downwards. As a result, the ray of light exits the block of glass with a path parallel to that which it entered the block but refracted at a higher point.