Lamp research. Researcher measuring the light output from a blue fluorescent lamp. This lamp was designed to provide different architectural lighting effects. Fluorescent lamps are much more efficient than filament light bulbs as less of the radiation is in the infrared. The electric current passing through the low pressure mercury vapour in the glass tube causes the gas to emit ultraviolet radiation. This is converted into visible light by phosphors, substances that produce light without being heated, on the inside of the tube. Photographed at Siemens' Osram Sylvania Laboratory in Beverly, Massachusetts, USA.