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Low-pressure Hg lamps can be rather small, but efficient sources of deep UV light. Low-pressure mercury-vapor lamps [15] usually have a quartz bulb in order to allow the transmission of short wavelength light. If synthetic quartz is used, then the transparency of the quartz is increased further and an emission line at 185 nm is observed also.
High pressure sodium lamps, producing up to 150 lumens per watt produce a broader light spectrum than the low pressure sodium lamps. Also used for street lighting, and for artificial photoassimilation for growing plants High pressure mercury-vapor lamps are the oldest high pressure lamp type and have been replaced in most applications by metal ...
A fluorescent lamp, or fluorescent tube, is a low-pressure mercury-vapor gas-discharge lamp that uses fluorescence to produce visible light. An electric current in the gas excites mercury vapor, to produce ultraviolet and make a phosphor coating in the lamp glow.
However, mercury-vapor lamps are falling out of favor and being replaced by sodium-vapor and metal-halide lamps. Metal-halide and ceramic metal-halide lamps can be made to give off neutral white light useful for applications where normal color appearance is critical, such as TV and movie production, indoor or nighttime sports games, automotive ...
Unsaturated mercury vapor can be used, but as it can not be replenished, the lifetime of such tubes is lower. [1] The strong dependence of vapor pressure on mercury temperature limits the environments the mercury-based tubes can operate in. In low-pressure mercury lamps, there is an optimum mercury pressure for the highest efficiency.
Ultra-high-performance lamp. An ultra-high-performance lamp, often known by the Philips trademark UHP, is a high-pressure mercury arc lamp. [1] These were originally known as ultra-high-pressure lamps, [2] [3] because the internal pressure can rise to as much as 200 atmospheres when the lamp reaches its operating temperature.
The F-H region is a region of glow discharge; the plasma emits a faint glow that occupies almost all the volume of the tube; most of the light is emitted by excited neutral atoms. The I-K region is a region of arc discharge; the plasma is concentrated in a narrow channel along the center of the tube; a great amount of radiation is produced.
Photochemical reactions require a light source that emits wavelengths corresponding to an electronic transition in the reactant. In the early experiments (and in everyday life), sunlight was the light source, although it is polychromatic. [7] Mercury-vapor lamps are more common in the laboratory. Low-pressure mercury-vapor lamps mainly emit at ...
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