Light-emitting diodes. Researcher's hand holding a palette containing the spectrum of light-emitting diodes (LEDs). LEDs are efficient converters of electric current into light that are used in electronics displays, vehicle dashboards and brake lights. They consist of two semiconductor layers spiked with impurities to give them opposite electrical properties. The first LEDs, which produced red or green light, were developed in the 1960s. Since then, orange, yellow, blue and white LEDs have been designed. Photographed at Siemens' Osram Sylvania Laboratory, Beverly, Massachusetts, USA.
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