Why are UK street lights amber?
Why are UK street lights amber?
Out of context: Reply #2
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- kelpie0
The low-pressure sodium lamp has remarkably high luminous efficiency, or efficacy, producing as much as 200 lumens per watt of input power. The radiation is nearly monochromatic yellow in color, and is used where color rendition is unimportant. The very high luminous efficacy is due to very stringent control of heat losses from the arc. The key to the heat conservation is the indium oxide film used to reflect infrared energy back to the arc tube and the evacuated outer jacket that minimizes the conducted thermal losses. Lamps at 18 and 10 W of power have been developed for very low-energy-cost uses. The 10-W lamp produces light at 100 lm/W.
something like that anyway