What causes a light-emitting diode (LED) to emit light?

A Light-Emitting Diode (LED) operates like a standard semiconductor diode, meaning it is designed to allow electricity to flow in only one direction. When a voltage is applied correctly—positive to the anode and negative to the cathode—a 'forward current' flows across the semiconductor junction, releasing energy in the form of photons (visible light). If the diode is connected backward, it blocks the electrical flow (except for a tiny, negligible reverse current), resulting in no light being emitted. Capacitively or inductively coupled RF signals are complex concepts completely unrelated to the basic direct current (DC) operation of an LED.