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Author Topic: Street Lights Start of White Then Turn Orange !!..what's that all about ?  (Read 9352 times)

Offline neilep

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Dearest Science Peeps who Know Stuff More Than Me,

Whilst I was parked outside a clients house of mine in South london on Sunday night

I could not help but stare agog and in awe filled with total amazement and wonder *

at the spectacular thrilling ** way the street lights came on. They first went pure brilliant white and then they turned ORANGE !!

Why's that then ?






* slight exaggeration

** even more slight exaggeration joy and luff !


 

Offline Ben6789

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heh, thanks for the references.

Mabybe their expermenting with differnt colors, instead of yellow, they use orange.
 

Offline science_guy

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I dont know about England, but in the USA, they use Green for go, you idiot, your holding up traffic, yellow for you should speed up to get by before it turns red, and red for stop, you numbskull, traffic is crossing the other way.
 

Offline Ben6789

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haha, thats about it. nailed it science_guy!
 

paul.fr

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so Neil, are you talkin street lighting or traffic lighting.  ???   ;)
 

Offline neilep

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Is it me or did I just imagine writing ' STREET LIGHTING' in my above post  ?

My clients house does not have traffic lights outside their house !!
 

paul.fr

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Is it me or did I just imagine writing ' STREET LIGHTING' in my above post  ?

My clients house does not have traffic lights outside their house !!

hence my question. maybe "others" were wondering what clients.....no
 

Offline daveshorts

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I have not seen them starting off white, although I have seem some that start red and then go yellow. This is because the yellow colour is from excited gaseous sodium atoms, which will emit strongly in the yellow part of the spectrum.

 Because at room temperature sodium is a solid, when the lamp is cold it doesn't have much in the way of sodium gas. Because of this they are filled with neon which is a gas at room temperature and allows the lamp to start up. When excited neon atoms glow red. As the lamp heats up the soidium evaporates and overpowers the quite weak neon light.

I guess the lamps you were looking at were filled with something that glowed white to start with ( krypton may do this if my memory serves ) which is then overpowered as the sodium comes on line.
 

Offline neilep

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I dont know about England, but in the USA, they use Green for go, you idiot, your holding up traffic, yellow for you should speed up to get by before it turns red, and red for stop, you numbskull, traffic is crossing the other way.

ha ha ha !! *falls over in the gutter laughing like a hysterical sardine*..LOL  ewe got me fair and square there Science_guy..

I am referring to STREET LIGHTS that light the street up....nothing to do with Traffic lights at all !
 

Offline neilep

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I have not seen them starting off white, although I have seem some that start red and then go yellow. This is because the yellow colour is from excited gaseous sodium atoms, which will emit strongly in the yellow part of the spectrum.

 Because at room temperature sodium is a solid, when the lamp is cold it doesn't have much in the way of sodium gas. Because of this they are filled with neon which is a gas at room temperature and allows the lamp to start up. When excited neon atoms glow red. As the lamp heats up the soidium evaporates and overpowers the quite weak neon light.

I guess the lamps you were looking at were filled with something that glowed white to start with ( krypton may do this if my memory serves ) which is then overpowered as the sodium comes on line.

THANKS for this Dave....yes..it was  very bright white light...and then within a couple of seconds turned orange...

THANKS

neil
 

Offline Soul Surfer

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Dave has most of the story but there are a couple of other interesting details.  Most sodium lamps these days are quite high pressure ones so they first show the colour of the starting gas then as they war mup go strongly yellow (the colour of the sodium D lines then as they warm up and the pressure builds up in the inner tube go a more golden orange due to the pressure broadening of the spectrum lines.  If you look at these with a spectroscope you will find that the actual range of frequencies is still quite small around the yellow region of the spectrum but you can still see strongly coloured objects in their approximate colour even though there is very little red green or blue light in the lamp output.  This is all due to the way we percieve colour as differences in respose from the colour sensors in our eyes.  The old low pressure sodium lamps were intensely yellow and didn't really show other colours at all.
 

Offline lightarrow

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They first went pure brilliant white and then they turned ORANGE !!
Why's that then ?
Maybe they substituted the kind of lamps in the meantime? ;)
 

Offline that mad man

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There are two main types of sodium lamps.

Low pressure called SOX: tubular and long @ 2-3 ft. These are the most efficient and used mainly on motorways and produce a noticeable orange colour.

High pressure called SON: these can be either shaped like a bulb or tubular @ 1 ft max.

They can start off with a whiteish glow and then turn orange, or orange and turn whiteish. This can depend on the age of the lamp as the older the lamp the more orange in colour it goes until it eventually fails.

The metallic sodium in the lamps takes a while to heat and turn to a gas so its a mainly white light to start off with and then it quickly turns orange.

Bee
« Last Edit: 03/05/2007 16:34:13 by that mad man »
 

Offline chris

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Why are the older type more efficient than the newer type? That sounds counter-intuitive. Or is it just in the name of more light from a relatively smaller unit?

Chris
 

Offline daveshorts

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An old fashioned soidium lamp emmits in a yellow part of the spectrum that is very close to the point where your eye is most sensitive, this means that for the same apparent brightness you can use less light. The problem is that because it emmits in only one frequency (technically 2 but they are very close together) you can't tell colours apart very well, so even though it is quite bright you would be better at distinguishing a pedestrian in lower intensity white light.

The high pressure sodium lamps run at a much higher pressure, this means that the sodium atoms are colliding more of the time, when two atoms collide they deform slightly altering their energy levels and allowing electrons to move between levels that would be normally disallowed.  This will alter the colour of light they emit. This means that they are not longer monochromatic so you can see colour in them. I guess because they are running hotter they will loose more heat by infra-red emmision and conduction, so they are less efficient - also because they are emmitting from a broader range of frequencies the odds some will be invisible.
 

Offline that mad man

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By older I meant the life of the lamp itself.

Low pressure is more efficient and lasts longer but is very orange so using them on a motorway makes sense. The colour don't matter much and because they last longer there is less cost in replacing them.

It reminds me of the old joke, "how many men does it take to change a lightbulb?" On a motorway it works out at around 6, takes several hours and costs a fortune!  ;)

High pressure is less efficient but smaller in size and is used mainly on street lighting as it has a broader spectrum. Its also used to light some important parts on motorways.

 

Offline Seany

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Hmm.. I always see it as orange when it is first turned on, or a red colour, then it gradually goes yellowy-white.
 

Offline iko

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Hmm.. I always see it as orange when it is first turned on, or a red colour, then it gradually goes yellowy-white.

Now confess Neilepus withdrawmisticus,

what did you drink that evening???  ;D

(Ooops! I just wrote a Seany-like sized post! ) [B)]

 

Offline Seany

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Gwrrr.. I will write long. OK?

Iko is mean
Iko is fussy
Iko is kind
Iko is funny
Iko is obsessed with Cod liver oil
Iko is obsessed with Garlic
Iko is called Enrico
Iko writes Ikod as his signature
Iko is weird
Iko is great ;D

Happy? ;D
 

Offline iko

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No No No Seany!!!

you just wrote 10 times the SAME word!
Even a short and meaningless one...damn,
What should we do to teach you how
to become a respected, educated,
polite and perfect "poster"?  ;D





 

Offline Seany

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Hahaa!! Techinally I wrote 10 times Iko and 9 times "is" SO HAAA! :P
 

Offline iko

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Hahaa!! Technically I wrote 10 times Iko and 9 times "is" SO HAAA! :P

Of course I'm teasing you, LittleBig Seany,
I'm sure your mum almost drowned in cod liver oil
when she was expecting you!  ;D

Quote
If you ask this fool on the hill which is the most amazing report about CLO in the recent past, he won't have any doubt:

Maternal supplementation with very-long-chain n-3 fatty acids during pregnancy
and lactation augments children's IQ at 4 years of age.


Helland IB, Smith L, Saarem K, Saugstad OD, Drevon CA.
Pediatrics. 2003 Jan;111(1):e39-44.

To read the abstract click down here:
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=12509593&query_hl=6&itool=pubmed_docsum

Pediatrics 2003, Norwegian research, scientifically sound:

Children more clever at 4yrs
with one spoon of CLO per day
during pregnancy and lactation!



Fig. 1. Scores on the K-ABC for children whose mothers had taken cod liver oil (n = 48) or corn oil (n = 36) during pregnancy and lactation. Values for the different subtests are shown. MPCOMP, Mental Processing Composite; SEQPROC, Sequential Processing; SIMPROC, Simultaneous Processing; NONVERB, Nonverbal Abilities.




Neat eh?
 
...when I've got this information my two sons had already grown up!
Some people could still make it with their children.
A good point to start a mini-review and/or discussion.


iko



« Last Edit: 04/05/2007 22:47:32 by iko »
 

Offline Seany

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*Smacks forehead*.. Yes..
 

Offline iko

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Gwrrr.. I will write long. OK?

Iko is mean
Iko is fussy
Iko is kind
Iko is funny
Iko is obsessed with Cod liver oil
Iko is obsessed with Garlic
Iko is called Enrico
Iko writes Ikod as his signature
Iko is weird
Iko is great ;D

Happy? ;D

All true, but I'm afraid
that you forgot the basics:

Iko is FISHY!  [^]

« Last Edit: 04/05/2007 12:35:27 by iko »
 

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