Fluorescent tubes

led tube light

These are low-pressure mercury vapor lamps that come in two versions: "hot cathodes" and "cold cathodes". The classic fluorescent tube used in offices and factories corresponds to the first version; the term "hot cathode" refers to priming the lamp by preheating the electrodes to create sufficient ionization of mercury gas and vapors to stabilize the discharge.

Fluorescent lamps require an external ballast for priming and stabilizing the current. In addition to the small amount of mercury vapor, they contain a starting gas.

The low pressure of the mercury causes a light emission discharge in the pale blue. Most of the radiation is in the ultraviolet zone at 254 nm, the characteristic mercury radiation frequency. The inner wall of the tube has a thin layer of fluorescent material that absorbs ultraviolet (UV) radiation and radiates energy in the form of visible light. The quality of the color of the light is determined by the fluorescent layer. There are different fluorescent substances emitting various colors and offering multiple color renditions.

In the 1950s, existing fluorescents offered the choice between reasonable light efficiency (60 lumens/watt) with poorer light in reds and blues, or better color rendition with "luxury" fluoresces, but of a lower yield (40 lumens/watt).

New narrow-band fluoresces were developed in the 1970s. They emitted separately in red, blue and green but, combined, they produced white light. A proportion of the proportions allowed to obtain a range of colored appearances all offering an excellent rendering of the colors. These substances used for three-band lamps are more efficient than older ones and are the most economical lighting solution, even if the lamps are more expensive. Improving efficiency reduces installation and operating costs.

The "three-band" principle has been extended to five-band lamps for applications requiring excellent color renderings, such as in art galleries and industrial chromaticity.
Modern narrow-band fluorescents offer greater durability, better lumen maintenance, and longer lamp life.

Compact fluorescent lamps


Due to its linear shape, the fluorescent tube is not intended in practice to replace the incandescent lamp. Narrow, small tubes can be configured to be about the same size as the incandescent lamp, but this imposes a much higher surface power density on the fluorescent substances. The use of three-band substances is essential to achieve acceptable lamp life

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