Various Lighting Devices and How they work


In the night we use artificial lights. For this purpose we use different types of devices like Bulbs, Tubes, CFLs, LEDs and so many others. Thought their basic idea is same, converting electrical energy into light energy, these devices achieve this goal using different techniques. Lets have a basic idea how they work.

Light Bulbs or Incandescent Bulbs


As the name says, Incandescent, "emitting light because of being heated" the basic idea of getting light by heating a resistance. Jule's law says when electric current flows through a conductor it gets heated. The amount of heat will mainly depend upon the current, time of flow and  the resistance of the conductor. So more the resistance more the heat. Thats the reason a high resistance thin wire of tungsten is used as a filament. When current flows through the filament it turns red hot and emits light. The filament needs to be protected from getting oxidized and fused by the environment so it's protected inside a glass tube filled with insert gas, like Argon.

Use
They are used in domestic Lighting purpose. Though they are being replaced by LEDs and other lamps because of high power consumption and small life of operation.

Tubes and CFLS or Fluorescent Lamps

The idea of creating an electric arc and then converting the light into visible light. A tube light has tungsten electrodes on the ends (tungsten because it has high melting point). First using a choke and a starter a high voltage is applied accross the electrodes. Once the gas inside the tube ionizes, choke cuts off and current flows through the tube creating and electrical spark. The spark emits ultraviolet light. A Fluorescent material is coated on the inner side of the tube. This material has a property called fluorescence , which absorbs high frequency Ultraviolet light and converts to low frequency visible light. CFLs and Mercury Vapour lamps work More or less the same way

Use
Domestic and office purpose. This lamps are more efficient than Incandescent lamps. Fluorescent lamps create problem in camera imaging. They are being replaced by LEDs now

LEDs

Materials conducting electricity are called Conductors, and noncunducting are called insulators. But there are materials that behave in between conductor and insulator and are called Semiductors ex  Garmenium Selenium etc. They conduct electricity due to impurity or temperature effects. Based on impurity they can be P type ( Having holes ) or N type (Having electrons, holes and electrons are opposite to each other). LEDs are diaodes (Light Emitting Diaodes)   having two parts P typ and N typ. When connected with Direct Current the electrons from the N typ side jump to the P typ side and while jumping they lose some amount of energy in the form of light.

Use

LEDs are very efficient. They are small compact easy to use and replacing almost every other typ of light bulbs from domestic to industrial everywhere. LEDs are also extensively used in TV and Mobile Phone Display.

Watch Video for visualise

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