Lighting


Lighting refers to the use of an artificial source of light for illumination. Lighting sources work either on the principle of incandescence (thermal excitation) or luminescence which have led to the development of two different families of sources tungsten or incandescent sources on one hand, discharge sources on the other hand. Part of the power input to the lighting unit is transformed into visible light, while the rest is considered as loss (heat).

It is a key element of architecture and interior design. Residential lighting uses mainly either incandescent lamps or fluorescent lamps and often depends heavily on movable fixtures plugged into outlets; built-in lighting is typically found in kitchens, bathrooms, and corridors and in the form of hanging pendants in dining rooms and sometimes recessed fixtures in living rooms. Lighting can be either indoor or outdoor. It can be for decorative purposes, for functional usage, for general lighting and also for entertainment purposes.

Various forms of lighting exist. Some major ones are, track lighting, recessed lighting, uplighting, down lighting, backlighting, ambient lighting, task lighting, etc. Lighting relies on many sources. Some of these include:

Incandescent lamps - consist of a bulb containing a wire filament which is heated and emits light. Incandescent lamps may have different types of bulb finishes to modify the brightness of the filament; internal reflecting substances on the bulb to control the direction of the light: halogen gases and special tungsten filament.

A fluorescent tube - is a low pressure discharge lamp which consists of a glass tube coated with phosphors, trace amounts of mercury and an electrode at each end of tube. Compact fluorescent lamps (CFLs) usually consist of 2 or 4 small fluorescent tubes with a plug-in base or they may be a self contained lamp (i.e. incorporating a ballast) with a screw in base or bayonet cap.

High intensity discharge lamps - consist of an arc tube in which the discharge occurs, surrounded by an outer envelope. They require control gear for starting and to maintain stable operating conditions. They fall into 3 distinct families: high pressure sodium (HPS), high pressure mercury (HPM) and metal halide (MH).

LED lighting is also catching up with the lighting market and is now a major force in lighting industry.

Lighting involves use of luminaries as well. This involves reflection using mirror optics. This increases efficacy and glare can be controlled properly. Lighting also involves lighting control systems that range from simple measures such as localised manual switches positioned close to the areas which they control, to more complex automatic systems based on time control, occupancy linking or photoelectric daylight linking. Thus lighting essentially is use of power to emit light through devices controlled via regulators.

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