Lamp research. Researcher measuring the emissions from an Endura fluorescent lamp. Fluorescent lamps are more efficient than filament light bulbs, and this bulb lasts for 100,000 hours. The electric current passing through the mercury vapour in the bulb causes the gas to emit ultraviolet radiation. This is converted into visible light by phosphors, substances that emit light without being heated, on the inside of the tube. The antennae (black sphere) measures electromagnetic emissions to ensure that the bulb does not interfere with electronic devices. Photographed at Siemens' Osram Sylvania Laboratory, Beverly, Massachusetts, USA.