Viewing a Corner Cube Prism: what one would see when looking in to a retro-reflector prism 👁. A light ray entering a mirrored corner cube prism always exits along a parallel path- but how would a camera capture this experience? Did I fool you? The geometry of a trihedral retroreflector is simply the corner of a cube, and arrays of corner-cubes like this one were placed on the Moon by Apollo astronauts to allowing precise measurement of the Earth-Moon distance by bouncing powerful laser pulses b