What is a Halogen Lamp? – Working Principle, Construction and Applications

A halogen lamp or tungsten halogen lamp is an incandescent lamp. The halogen lamp consists of a tungsten filament enclosed in an environment of an inert gas like argon and a small amount of a halogen like bromine or iodine. The combination of the tungsten filament and the halogen results in a chemical reaction (called regenerative cycle or halogen cycle).

This regenerative cycle increases the life span of the filament. Also, the halogen cycle prevents the darkening of the lamp envelope by redepositing the tungsten from the inside of the lamp back onto the filament.

Working Principle of Halogen Lamp

The working of the halogen lamp is based on the principle of thermal radiator, i.e. light is produced by heating a solid to a very high temperature. The brightness of the emitted light is proportional to the heating temperature. The halogen lamps have continuous spectral output. A major portion, up to 85%, of the light emitted by the halogen lamps lies in the infrared region, around 15% to 20% lies in the visible region and less than 1% lies in the ultraviolet region

Construction of Halogen Lamp

The construction of the tungsten halogen lamp is shown in the figure.

The halogen lamp consists of a filament of tungsten metal, which is enclosed in a fused silica quartz glass. This glass cover of the lamp is filled with an inert gas like argon and nitrogen. There are two terminal leads connected to the lamp filament for supply the power to the filament.

The use of halogen gas at low pressure in the lamp reduces the uneven evaporation of the filament and darkening of the glass cover. The halogen lamps can operate at a higher temperature than a standard gas filled incandescent lamp of the similar power rating without loss of its operating life.

Advantages of Halogen Lamp

The primary advantages of the halogen lamps are given as −

• Halogen lamps have long life, around 2000 to 4000 hours.

• Halogen lamps are smaller in size.

• These lamps produce better color radiation.

• Halogen lamps has no blackening of lamp, thus there is no depreciation of lumens output.

• Halogen lamps have high operating temperature with increased luminous efficiency.

Applications of Halogen Lamps

Some applications of the halogen lamps are given below.

• Halogen lamps are widely used in automobiles as headlamps.

• Halogen lamps were used on the Times Square Ball.

• They are used as an infrared light source.

• Halogen lamps are also used in stage lighting.

• These lamps are also used as projection lamps in motion pictures and slide projectors.