Mercury Vapor lamps are definitly much better for illumination.
I dont know how many ppl here are aware, but in all refineries/chemical plants/industrial areas/workshops they use MV for illumination.
MV's give a white light, with slight purple/violet tinge. Which is anyway more indicative of true color. Whereas the Sodium vapor gives only that orange wavelength - which doesnt allow you to see true color.
The only reason why Na lamps are used is because of low running cost - they consume less electricity.
Actually the ones that we see eon raods are the low pressure sodium vapor lamps. The high pressure ones give a better color range - with pink tinge. But I dunno exactly why they aint used over here in India. |