What is a Light Emitting Diode (LED)?

A Light Emitting Diode (LED) is best described as a semiconductor that emits light when an electric current passes through it. This phenomenon occurs due to a process called electroluminescence, where electrons recombine with holes within the device, releasing energy in the form of photons, which we perceive as light. LEDs are widely used in various applications, from indicator lights and display screens to general lighting and automotive lighting, due to their efficiency, longevity, and versatility.

Other options suggest varying concepts that do not apply to LEDs. Describing it as a mechanical device does not capture its electronic nature or operational principle. Identifying it as a type of battery is incorrect, as LEDs are not power sources; rather, they require external power to function. Additionally, describing an LED as a sensor for detecting light also misses the mark, as LEDs primarily serve as sources of light rather than as detectors. Thus, the identification of an LED as a semiconductor that emits light aligns precisely with its fundamental characteristics and function.