General Lighting Services refer to the glass bulbs, filled with gas, which have been used for lighting application many years ago and are still the most common type household lighting. They are sometimes called as incandescence lamp. The light comes from a wire filament, which heats up to incandescence. The filament contains inside the glass bulb integral with metal base. Light yield and color temperature increasing temperature. Hower, the service life of the lamp decreases as the tungsten wire evapo-rates and becomes more and more thinner.
The first incandescent lamp filament were carbon type and operated in a sealed vacuum with a luminous efficacy up to 4 lm/W. Efficacy was increased by the use of first tantalum as filament material and then tungsten in about 1910, still operating in a vacuum to exclude ixygen and to increase the operating temperature, since the higher the temperature, the higher the light output.
Fluorescent lamp and Compact fluorescent lamp are low pressure mercury discharge lamp. Upon the flow of the electrical charge, ultraviolet radiation will be produced, stimulates the phosphors on the inside of the fluorescent tube to product light by convert the UV radiation into visible light. As different phosphors give out different color appearances, so as the color temperature and the selection of correct control gear.
Usually in tubular form and need a ballast for operation which may be either a magnetic transformer or an electronic type. The “high efficiency” range for fluorescent lamp has been optimized to the highest light yield.
The light is formed from an arc discharge between two closely spaced electrodes sealed inside a small quartz tubular glass envelope capsule. Under normal operation, they require ballasts, which supply proper voltage and control current. The amount of light produced is greater than a halogen bulb, while consuming less power.
In all High Intensity Discharge lamps, that is Mercury Vapour, Metal Halide and High Pressure Sodium lamp, light is produced by the flow of a current through a metal vapor. Free electrons collide with an atom in the vapor instantaneously knock an electron into a higher energy level of the atom.