Question

What is a light-emitting diode (LED)? Write down one application of it.

Hint:

LEDs consume less power and produce less heat compared to traditional incandescent bulbs.

Answer 1

Step 1: When a Light Emitting Diode (LED) is forward biased, the applied voltage reduces the potential barrier at the p-n junction, allowing electrons from the n-region and holes from the p-region to move toward the junction. At the junction, electrons and holes recombine. During this recombination process, the electrons drop from a higher energy level to a lower energy level, and the excess energy is released in the form of photons (light). This phenomenon is known as electroluminescence.
Step 2: The color of the emitted light depends on the bandgap energy of the semiconductor material used in the LED. Different materials emit different wavelengths (colors) of light. For example:

Gallium arsenide (GaAs) emits infrared light,
Gallium phosphide (GaP) emits green or red light,
Gallium nitride (GaN) emits blue or white light.
By choosing appropriate semiconductor materials and doping levels, LEDs can be designed to emit a wide range of colors.
Step 3: LEDs are highly energy-efficient, converting most of the electrical energy into light with minimal heat loss. They also have a long operational life, are compact in size, and offer fast switching capabilities. Due to these advantages, LEDs are widely used in various applications such as display systems, indicator lights, lighting solutions, remote controls, and digital signage.