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Low-pressure Hg lamps can be rather small, but efficient sources of deep UV light. Low-pressure mercury-vapor lamps [16] 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.
Hewitt's lamp glowed when an electric current was passed through mercury vapor at a low pressure. Unlike Moore's lamps, Hewitt's were manufactured in standardized sizes and operated at low voltages. The mercury-vapor lamp was superior to the incandescent lamps of the time in terms of energy efficiency, but the blue-green light it produced ...
Mercury vapor: Light blue, intense ultraviolet: Ultraviolet not shown on this spectral image. Used in combination with phosphors used to generate many colors of light. Widely used in mercury-vapor lamps and fluorescent tubes. Sodium vapor (low pressure) Bright orange-yellow: Widely used in sodium-vapor lamps.
A high-pressure sodium street light in Toronto A high-pressure sodium-vapor lamp An HPS lamp that isn't entirely off. A sodium-vapor lamp is a gas-discharge lamp that uses sodium in an excited state to produce light at a characteristic wavelength near 589 nm. Two varieties of such lamps exist: low pressure and high pressure.
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.
The plasma of excited mercury atoms inside the lamp emits ultraviolet light directly. The lamps are coated on the inside with special phosphors. Unlike high-pressure lamps, the glass that is used in low-pressure lamps filters out all UVC. Once the plasma is fully formed, the plasma strips away the outer electrons from the mercury; when these ...