laser

Lasers produce an intense beam of single colour light. Laser light is different to other kinds of light because the light is coherent, all the waves are in step with each other, like a column of marching soldiers. In ordinary light the waves are disorganised like pedestrians on a crosswalk. The unique nature of laser light allows it to cut steel or make holograms, something that ordinary light can't do. Light is an acronym of 'Light Amplification by Stimulated Emission of Radiation'. The first laser was constructed in 1960. It was a ruby laser like the illustration above.

It consisted of a synthetic ruby rod polished and silvered at both ends. A flash tube similar to the ones used for photography surrounded the rod. As the flash tube flashed light travelled back and forth within the ruby rod being reflected by the mirrors, gaining strength with each pass. Eventually some of the light was allowed to escape from one end to give a short burst of intense red light.