Light emitting diodes, commonly called LEDs, are one of the important inventions in the electronic world but we have not heard much of them. They do dozens of different jobs and are found in all kinds of devices. Among other things, they form the numbers on digital clocks, transmit information from remote controls, light up watches and tell you when your appliances are turned on. Collected together, they can form images on a jumbo television screen or illuminate a traffic light. Basically, LEDs are just tiny light bulbs that fit easily into an electrical circuit. But unlike ordinary incandescent bulbs, they don’t have a filament that will burn out, and they don’t get especially hot. They are illuminated solely by the movement of electrons in a semiconductor material, and they last just as long as a standard transistor.

UNDERSTANDING DIODE
A diode is the simplest sort of semiconductor device. In the case of LEDs, the conductor material is typically aluminum-gallium-arsenide. In pure aluminum-gallium-arsenide, all of the atoms bond perfectly to their neighbors, leaving no free electrons (negatively-charged particles) to conduct electric current.

DIODE AND LIGHT
Light is a form of energy that can be released by an atom. It is made up of many small particles like packets that have energy and momentum but no mass. These particles, called photons, are the most basic units of light. Photons are released as a result of moving electrons. In an atom, electrons move in orbital’s around the nucleus. Electrons in different orbitals have different amounts of energy. Generally speaking, electrons with greater energy move in orbital’s farther away from the nucleus. For an electron to jump from a lower orbital to a higher orbital, something has to boost its energy level. Conversely, an electron releases energy when it drops from a higher orbital to a lower one. This energy is released in the form of a photon. A greater energy drop releases a higher-energy photon, which is characterized by a higher frequency. The atoms in a standard silicon diode, for example, are arranged in such a way that the electron drops a rel-atively short distance. As a result, the photon's frequency is so low that it is invisible to the human eye —it is in the infrared portion of the light spectrum.

WHY LED
LEDs are specially constructed to release a large number of photons outward. Additionally, they are housed in a plastic bulb that concentrates the light in a particular direction. LEDs have several advantages over conventional incandescent lamps. For one thing, they don’t have a filament that will burn out, so they last much longer. Additionally, their small plastic bulb makes them a lot more durable. They also fit more easily into modern electronic circuits. But the main advantage is efficiency. LEDs generate very little heat. Until recently, LEDs were too expensive to use for most lighting applications because they were built around advanced semiconductor material. The price of semiconductor devices has plummeted over the past decade, however, making LEDs a more cost-effective lighting option for a wide range of situations. While they may be more expensive than-incandescent lights up front, their lower cost in the long run can make them a better buy.