High-powered bulb. At full brightness, this arc lamp bulb generates light using thousands of watts of power. It will be used in sports stadiums for evening games. Arc lamps use the bright light emitted by an electric arc (red, yellow & green), a stream of electrons travelling between two electrodes. The arc is colour coded from red (hottest) through yellow to green (coolest). The central cylinder through which the arc is flowing contains halogen gas. Photographed at Siemens' Osram Sylvania Laboratory in Beverly, Massachusetts, USA.