Science stuff

stu

This is probibly the wierdest off topic post here but Im kind of desperate. I have this science assignment that has to be in on Friday and I cant figure out on of the questions.
So this is it:

Fluorescent light tubes bought in England usually give a slightly yellow light. But flourescent tubes bought in Saudi Arabia give a slightly bluish light. Suggest why they are made with these differences.

I thought it might be because of the common colours that are in each country. So that more can be seen in the dark because of light refection off objects and what not.

If anyone has any other ideas that would be really cool.

AlanRatcliffe

Educated guess would be the different colour of the natural daylight in those countries. Britain is a lot cloudier and the sunlight travels through more atmosphere, so the light is shifted towards yellow/red side of the spectrum, while in clear cloudless Saudi Arabia where the atmosphere is thin, the sky is blue and the light is shifted to the blue spectrum.

PeteM

It could be for aesthetic/psychological reasons. In a colder climate a warm light is more comforting and in a warm climate a cool light is more refreshing.

vic

The scientific answer may lie here....different phosphorous salts used in the different tubes.....
http://en.wikipedia.org/wiki/Fluorescent_lamp

Phosphor composition
Some of the least pleasant light comes from tubes containing the older halophosphate type phosphors (chemical formula Ca5(PO4)3(F, Cl):Sb3+, Mn2+). The bad color reproduction is due to the fact that this phosphor mainly emits yellow and blue light, and relatively little green and red. In the absence of a reference, this mixture appears white to the eye, but the light has an incomplete spectrum. The CRI of such lamps is around 60.

Since the 1990s, higher quality fluorescent lamps use either a higher CRI halophosphate coating, or a triphosphor mixture, based on europium and terbium ions, that have emission bands more evenly distributed over the spectrum of visible light. High CRI halophosphate and triphosphor tubes give a more natural color reproduction to the human eye. The CRI of such lamps is typically 82–100.

The basics are the following: Electricity activates mercury vapour (Hg) in the lamp which emits ultraviolet radiation. This UV in turn excites the flourescent material coated on the inside of the lamp. This material is a mixture of phosphorous salts. Depending on the nature (chemical composition) of the mix a certain colour light will be emitted. One mix will say emit light with a stronger yellow component whilst another mix will emit more blue.
I really don't think that "where you buy the tube" has anything to do with the answer to the question or task you've been given... :?

Now go and finish your project young man.... ?

MikeM

I do know the tint of the hue affects circadian rhythms as well as quality of sleep so it can definately be controlled (Going from pink to blue)

But I agree with Alan and Pete in this case ?

AlanRatcliffe

No specific answer here, but some good info that may help you draw your own conclusions: http://nemesis.lonestar.org/reference/electricity/fluorescent/lamps.html

vic

Stu...what is interesting is that in SA you get the so-called energy saving bulbs...same thing...these also emit either a blueish light or a yellowish light...so it really boils down to the composition of the phosphorous material on the inside of the lamp.
Alans 1st post above also makes sense as an add-on to your project. But I think the basics of operation of the tubes needs to be explained up front.

inflames

Was it a guitarist or a drummer that changed the bulb? :-\

vic

inflames wrote Was it a guitarist or a drummer that changed the bulb? :-\

Normally concertina players do those silly jobs.... ?

PeteM

joel wrote
? Your answer here :

http://members.misty.com/don/f-spec.html

A lot of technical info here regarding colour temperatures, but still does not address the assignment, "Fluorescent light tubes bought in England usually give a slightly yellow light. But flourescent tubes bought in Saudi Arabia give a slightly bluish light. Suggest why they are made with these differences."

vic

PeteM wrote
joel wrote
? Your answer here :

http://members.misty.com/don/f-spec.html
A lot of technical info here regarding colour temperatures, but still does not address the assignment, "Fluorescent light tubes bought in England usually give a slightly yellow light. But flourescent tubes bought in Saudi Arabia give a slightly bluish light. Suggest why they are made with these differences."

I have been thinking about this question all night...and I hope that Stu will give us the answer that the teacher has in mind. This is a science task and from what I gather certainly not an interior design project ? One could then also ask..."why is the light in certain parts of Amsterdam of a reddish colour"..... ?

From an interior design perspective one could argue that a yellowish light (warm colour) would be more pleasing in cold England while a blueish light (cool colour) in hot Arabia will be more apt that a yellow one...? no, it can't be that simple ! ?

PeteM

vic wrote This is a science task and from what I gather certainly not an interior design project ?

The point might be that the end user should be taken into account when designing and making a product. I.e. That market demand has a bearing on the application of science. E.g. why design and manufacture a P90 and a Humbucker? - surely, one pickup will do. ?

vic wrote "why is the light in certain parts of Amsterdam of a reddish colour"..... ?

For ultimate consumer comfort. ?

AlanRatcliffe

vic wrote This is a science task and from what I gather certainly not an interior design project ?

I'm guessing you don't have much experience with "Outcomes Based" Education (OBE)? Stick to the scientific facts and some ~~children~~ umm... ~~pupils~~ ah... ~~students~~ err... learners might (gasp!) fail! That might make them feel inferior and scar them for life! So what if they don't actually learn anything and are totally unprepared for the real world - they could always come work in the education department.

(Sorry... I've seen and worked on a lot of the OBE textbooks - my wife is in the industry)

vic

@Stu....why are you so damn quiet...c'mon what do you think of all the stuff that we have been crammin' our grey cells with...!
@Alan....I would not be surprised if what you say about OBE is real. I am still lecturing and have experienced to some extent what you are referring to...especially at 1st year level.
@PeteM.......+3 ?

vic

Good night Stu....and good luck with your task...

stu

LOL ? @ Alan

Thanks for all the opinions. If I dont get a solid answer this thread will deffinatly help me come up with something.
Im doing my matric through a correspondence so I have no clue who wrote the assignment so I wont be able to ask them what they wanted for that question.
However I got my friend who does got to school to as his science educator what he/she thinks. So I will see what he comes up with tomorrow and I will let you guys know.

I think its got something to do with light reflection. Because objects absorb all colours exept thier own. So if an object that is red has a red, white or megenta light shine it it will reflect red because those colours contain red. But if it where a blue light it would look black because it abosrb all the light and blue does not contain red so it did not reflect any red. Or something like that....

So the yellow light is used England so that things that contain the colours red and green will show up well.
But I dont see why colours in England would be that differant to colours in Saudi Arabia

AlanRatcliffe

stu wrote But I dont see why colours in England would be that differant to colours in Saudi Arabia

The same reason the sky is blue and a sunset is red. Look up "Rayleigh scattering" and try figure out the rest yourself - or you're not actually learning anything.

TomCat

OK...here is what I think.

In Saudi Arabia the local population (Men) wear mostly white clothing. The more blue spectrum of the light make their clothes look cleaner as the blue excites the whitening agents used in detergents. The yellow spectrum lights in the UK would make their clothes look "dirty".

Off the wall I know....but you never know......