The light that falls is refracted specifically, allowing us to see a rainbow effect on the cold cut's surface. The natural muscle structure, composed of many thin fibres, acts like a prism ...

The prism bends different colours of light at different angles ... the sun is behind you and the rain in front of you, you see a rainbow of colours reflected back from inside the raindrops.

An upside down "rainbow" has been spotted ... at such an angle that light enters through a flat top face and exits through a side prism face. It said the arcs were "actually quite common", being ...