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sodium-vapour lamp

a type of electric lamp consisting of a glass tube containing neon and sodium vapour at low pressure through which an electric current is passed to give an orange light. They are used in street lighting
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
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Encyclopedia Article for sodium-vapour lamp

electric discharge lamp using ionized sodium, used for street lighting and other illumination. A low-pressure sodium-vapour lamp consists of a glass shell with metal electrodes, filled with neon gas and a little sodium. When current passes between the electrodes, it ionizes the neon, giving a red glow, until the hot gas vaporizes the sodium. This ionizes and shines a nearly monochrome yellow. High-pressure sodium-vapour lamps, made with a mixture of mercury and sodium, give a whiter light and are used for extra-bright lighting in places such as road intersections and sports stadiums

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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