There are actually two kinds of Na lights, high and low pressure. The low pressure ones are mostly a line spectrum and look darkish orange. In the high pressure ones, the Na lines are strongly pressure broadened and give a lighter orange color.
http://en.wikipedia.org/wiki/Sodium-vapor_lamp In a similar vein, Prof. Norman Ramsey at Harvard built a GIANT atomic clock experiment in an aluminum tank maybe 6' in diameter and 8' long. By the 1980s it had ceased to be used for experiments and was a giant equipment cupboard in the lab. The tank was enclosed in a giant plywood box with insulation. It eventually took a guy a couple of days with a Sawzall to cut it in half to get it out of the basement when he retired! http://en.wikipedia.org/wiki/Norman_Foster_Ramsey,_Jr. -John ============== > Hi Steve,They do use them in the USA.The advantages are,1 High efficiency2 > Better visibility in rain and fog. As there is only one main colour you do > not get diffraction rainbows.3 Kind to astronomers. A simple narrow stop band optical filter allows astronomers to remove the light pollution. In some areas around observatories they are mandated by local planning regulations. > These are considered to outweigh the disadvantage of no colour rendition. > Robert G8RPI. > > --- On Sun, 31/1/10, Steve Rooke <[email protected]> wrote: > > From: Steve Rooke <[email protected]> > Subject: Re: [time-nuts] [OT] Ikea Lamp > To: "Discussion of precise time and frequency measurement" > <[email protected]> > Date: Sunday, 31 January, 2010, 9:19 > > Not wishing to push this O/T thread more O/T but coming from England, and now in New Zealand, we have these sodium streetlights which I think are a pain in the neck. They have only two narrow spectra of yellow light and although they produce light it makes it hard, if not impossible, to make out colours. I wonder if they are being used in other members countries? > > Steve > > 2010/1/31 Dave Martindale <[email protected]>: >> If you care about accurate colour rendering, stick with incandescent, preferably halogen. "White" LEDs are actually blue LEDs coated with a phosphor that absorbs some of the blue light and emits approximately yellow >> instead. If you look at the spectrum, you'll see a broad yellow peak and a >> narrower blue peak. Your eyes see it as approximately white, but it's deficient in red and green compared to a black body emitter like hot tungsten. On the other hand, it's not as spiky as the output of fluorescents. > > -- > Steve Rooke - ZL3TUV & G8KVD > A man with one clock knows what time it is; > A man with two clocks is never quite sure. > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > > > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
