LED Citrine mirror lamp, 20 cm diameter. USB 3.5 Volt without adapter.

A led (from the English light-emitting diode) is an electronic semiconductor component constructed as a diode that emits light when current passes in the forward direction. This can be visible light in various colors, but also infrared radiation or ultraviolet radiation. After their invention in 1962, leds were initially only used as indicator lamps and for signal transmission. As a result of technological improvements, the light output has increased and at the end of the 1990s, leds could be produced that were suitable as a light source for normal daily use. Usually, a led is built into a small transparent housing of a few millimeters in size, which also functions as a lens.