[time-nuts] [OT] Ikea Lamp

J. Forster jfor at quik.com
Sun Jan 31 17:03:12 UTC 2010


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 <sar10538 at gmail.com> wrote:
>
> From: Steve Rooke <sar10538 at gmail.com>
> Subject: Re: [time-nuts] [OT] Ikea Lamp
> To: "Discussion of precise time and frequency measurement"
> <time-nuts at febo.com>
> 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 <dave.martindale at gmail.com>:
>> 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.
>
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