VOLKER STEGER / SIEMENS / SCIENCE PHOTO LIBRARY VOLKER STEGER / SIEMENS / SCIENCE PHOTO LIBRARY
Lamp research. Researcher using an Ulbricht, or integrating, sphere to study the light from an Endura fluorescent lamp. Once closed, the sphere's reflective inner surface allows the intensity of the lamp to be found using a sensor. Fluorescent lamps are more efficient than filament light bulbs, and the Endura lamp lasts for 100,000 hours. The electric current passing through the mercury vapour in the tube causes the gas to emit ultraviolet radiation. This is re-emitted as visible light by the phosphors on the inside of the tube. Photographed at Siemens' Osram Sylvania Laboratory in Beverly, Massachusetts, USA.
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