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Can a "white piece of paper" reflect light???

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I don't even know if that termed correctly..

 

Can a plain piece of " typing" paper " " white paper" held up to a light source reflect visible light frequencies and can these "colors be visually seen by an observer?

 

 

 

 

Ive read:

 

White surfaces are composed of molecules or atoms that don’t absorb any of the visible colors of light.

 

 

 

--->"But" those are surfaces not paper, is this correct to compare???

Edited by Iwonderaboutthings

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"But" those are surfaces not paper, is this correct to compare???

Does a white sheet of paper have a surface? If so, what colour is it?

 

How would the answer affect your reasoning?

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White sheets of paper, white bedsheets, white sheets of plastic, the situation is the same and you can compare.

 

White bodies reflect all wavelenghts of visible light.

 

Coloured bodies remove some of the wavelengths so the colour you see is what is left and reflected.

 

The difference between a mirror, which also reflects all wavelenghts and a white body is that mirror reflection is called specular reflection.

 

The surface of a mirror is smooth at the microscopic dimension sizes of light wavelengths, the surface of a white body is rough.

This means that the light from a mirror reflects in an organised fashion, whereas the light form a white body bounces off in random directions.

 

https://www.google.co.uk/images?hl=en-GB&q=specular+reflection&gbv=2&sa=X&oi=image_result_group&ei=I0lGU5OBK8rdPauFgLAM&ved=0CC4QsAQ

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Does a white sheet of paper have a surface? If so, what colour is it?

 

How would the answer affect your reasoning?

Well, a white sheet of paper really has 2 surfaces,IE front and back, the color I see them is white unless of coarse I paint on it.

 

I am not sure what link this is from here , but it stated something interesting:

 

 

papers impregnated with a chemical capable of absorbing one or more of the colors of white light. Such chemicals that are capable of selectively absorbing one or more frequency of white light are known as pigments

 

 

 

Now, I keep thinking glow in the dark affects with paper but am not sure...

White sheets of paper, white bedsheets, white sheets of plastic, the situation is the same and you can compare.

 

White bodies reflect all wavelenghts of visible light.

 

Coloured bodies remove some of the wavelengths so the colour you see is what is left and reflected.

 

The difference between a mirror, which also reflects all wavelenghts and a white body is that mirror reflection is called specular reflection.

 

The surface of a mirror is smooth at the microscopic dimension sizes of light wavelengths, the surface of a white body is rough.

This means that the light from a mirror reflects in an organised fashion, whereas the light form a white body bounces off in random directions.

 

https://www.google.co.uk/images?hl=en-GB&q=specular+reflection&gbv=2&sa=X&oi=image_result_group&ei=I0lGU5OBK8rdPauFgLAM&ved=0CC4QsAQ

thanks for the link I saw some information on specular reflections..

 

So, say a person paints on a white peace of paper as an expression of art.

 

Are you saying that they are painting in black paint " only ?"

 

You said that white paper " bodies" reflects all the colors in the color spectrum so I assume the colors are predefined " before paint is applied and the art work perceived as color and beauty.."

 

 

I reasoned this from your reply:

 

mirror reflects in an organised fashion

 

 

 

 

Where is the scientific proof that the peace of paper is " white" ?

But how can white be a color then????

 

That would imply that neither is the black paint either...

 

 

I believe there is something wrong here...

Edited by Iwonderaboutthings

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But how can white be a color then????

 

You need to understand what is color in the first place.

 

White light are photons with various frequencies in visible range. In wavelengths from 380 nm to 750 nm.

 

When photon hits surface of material, it can be absorbed or absorbed and emitted.

Emission can be in different range than absorption f.e. absorb ultraviolet and emit visible light.

 

White surface in white light is white, because all photons are reflected. Pretty none are absorbed.

If source of light is not white (some frequencies will be missing), white surface won't appear white to our eyes.

If you have red source of light (like in old fashion photographer room), white wall will appear red (wavelengths 380nm to ~600nm are missing).

 

Red surface in white light is red, because red photons (~620nm - 750 nm wavelengths) are reflected from it, and all others are absorbed.

 

Green grass and leafs in white light is green, because green photons (~500 nm... 570 nm wavelengths) are reflected, and all others are absorbed (and used in photosynthesis).

 

Color of material tells us how material reacts to photons with given frequency/wavelength/energy.

 

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I don't even know if that termed correctly..

 

Can a plain piece of " typing" paper " " white paper" held up to a light source reflect visible light frequencies and can these "colors be visually seen by an observer?

 

 

Yes. Shine colored light on white paper. You will see a colored area where the light is reflecting.

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Where is the scientific proof that the peace of paper is " white" ?

But how can white be a color then????

 

That would imply that neither is the black paint either...

 

 

I believe there is something wrong here...

 

 

Yes, there's something missing! Which is the physiology and neuroscience of colour perception.

 

"White" is what we call something that is a) bright and b) not one colour more than any other. If you have a white -painted wall, and you project a black and white image on to it using a projector, the parts of the white wall that receive the white parts of the image will now look brighter than the parts that don't, although you will "read" those parts as "black".

 

And if you do the same with a black-painted wall, just the same will happen - the brighter parts will read as "white", the dimmer parts as "black".

 

What the black wall and the white wall have in common is that they reflect all parts of the visible spectrum more-or-less equally.

 

However, the brain is even cleverer than that - if you project your image on to a red wall, after a while you will also "read" it as "black and white". That's because your brain rapidly "discounts" the red. If you look at the world through a red filter (say a red lighting gel) most things will look, at first, in shades of light and dark red. After a while, white things will look white, and black things black, and everything else, shades of grey. Interestingly, bright red things will look white! That's because only red light from the white things will get through the gel, and of course, only red light from the red things will get through too! So they will look identical - but read as "white", at least after a while, in both cases.

colour-constancy.png

 

 

Now look at this! The colours below are the actual colours of their corresponding pictures above. In the yellow-filtered image, yellow looks red, and grey looks blue. In the blue filtered image, purple looks red and grey looks yellow.

 

And that's before we even start on the different kinds of colour receptors in the retina....

Edited by Lizzie L

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Im not sure about reflecting light, however today it was rather sunny outside and I was sitting at the window going over some papers, and after looking at the paper for a few minutes I looked up and I was partially blinded for a minute due to the light reflections, I did a small experiment to see how long I would have to look at the paper to cause this, and it was not long around 30 seconds was enough.

I would say yes.

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Well I, for one, don't understand the coloured blocks or what you are saying about them Lizzie.

What should I be seeing on these blocks?

Edited by studiot

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Well I, for one, don't understand the coloured blocks or what you are saying about them Lizzie.

 

Heh, sorry.

 

OK, the two pictures are supposed to be of the same block, one seen through a partial yellow filter, one through a partial blue filter.

 

Looking at the upper surface, nearest row, we "read" the colours as: Blue, Yellow, Red, Blue, Green in both cases, albeit the ones on the left with a yellowish tinge and the ones on the right with a blueish tinge.

 

 

But in the left hand picture, the "blue " squares are actually "printed" in (i.e. use the same RGB recipe as) the grey squares in the diagram below, and the "red" squares are actually "yellow".

 

In the right hand pictures, the "yellow" squares are actually "printed" in grey, and the "red" squares in purple.

 

If you copy the picture into Paint, or some other image program you will see that the filled-in squares in the diagrams below correspond exactly to their counterparts in the picture above.

 

Effectively we mentally (or neurally) "subtract" yellow from the colours in the left picture, so that grey "reads" as blue, and yellow as red, while on the right we mentally subtract blue from all colours so that grey reads as yellow and purple as red.

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Thank you for further explanation, Lizzie.

 

The bottom row second square in (yellow) from left my dropper reads

 

R = 250

G = 230

B = 050

 

For the left hand block

 

R = 140

G = 150

B = 155

 

For the right hand block.

 

Is that what you mean?

 

I am still trying to absorb the implications of this.

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post-103802-0-70604800-1397243081_thumb.png

 

Does this help?

 

I used the color dropper in Paint to pick up the colour of the blue and red squares on the upper surface of the yellow-filtered image, and the yellow and red squares from the blue-filtered image, then used that colour to draw lines from the squares to the corresponding cells in the line drawings below. Lines, squares and cells in the line drawings are all the same colour. Each line to my eye appears to change colour as you move along it! But the colors are the same throughout.

 

The "blue" square in the yellow picture has RGB values of 142 149 155 and shows up as grey in the line drawing below (my leftmost line).

The "yellow" square in the blue picture also has RGB values of 142 149 155 and also shows up as grey in the line drawing below (my second from the right line).

 

The "red" square in the yellow picture has RGB values of 243 154 52, and shows up as yellow (orangey-yellow) in the line drawing below (my second from the left line)

The "red" square in the blue picture has RGB values of 150 55 147, and shows up as purple in the line drawing below (my rightmost line)

 

ETA: for some reason the picture renders rather small in the post - try clicking on it to see it full size.


Here's another famous one, just for black and white:

 

checkercomp.jpg

 

 

The squares A and B are exactly the same shade of mid grey (RGB 126 126 126). But A "reads" as black and B as white.


And another lovely one:

 

media_127556_en.gif

 

 

In the picture on the left you see pale blue spirals and lime green spirals, right? But they are both the same colour! On the right is the same picture with the pink and yellow replaced by black, leaving just one other colour, a fairly ordinary green.

Edited by Lizzie L

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Of course a white piece of paper can reflect light. If it did not, you would not be able to see it at all.

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Yes. Shine colored light on white paper. You will see a colored area where the light is reflecting.

If " a white piece of typing paper" "did" reveal colors of reds, pinks, blues and orange" "WITH WHITE LIGHT ONLY" and people saw this physically on the white typing paper..

 

WHAT WOULD THAT MEAN???

 

I know it has something to do with transmission, but remember we are talking about white light from light bulbs and even from the sun with a plain peace of white typing paper...

attachicon.gifRubikColorIllusion.png

 

Does this help?

 

I used the color dropper in Paint to pick up the colour of the blue and red squares on the upper surface of the yellow-filtered image, and the yellow and red squares from the blue-filtered image, then used that colour to draw lines from the squares to the corresponding cells in the line drawings below. Lines, squares and cells in the line drawings are all the same colour. Each line to my eye appears to change colour as you move along it! But the colors are the same throughout.

 

The "blue" square in the yellow picture has RGB values of 142 149 155 and shows up as grey in the line drawing below (my leftmost line).

The "yellow" square in the blue picture also has RGB values of 142 149 155 and also shows up as grey in the line drawing below (my second from the right line).

 

The "red" square in the yellow picture has RGB values of 243 154 52, and shows up as yellow (orangey-yellow) in the line drawing below (my second from the left line)

The "red" square in the blue picture has RGB values of 150 55 147, and shows up as purple in the line drawing below (my rightmost line)

 

ETA: for some reason the picture renders rather small in the post - try clicking on it to see it full size.

Here's another famous one, just for black and white:

 

checkercomp.jpg

 

 

The squares A and B are exactly the same shade of mid grey (RGB 126 126 126). But A "reads" as black and B as white.

And another lovely one:

 

media_127556_en.gif

 

 

In the picture on the left you see pale blue spirals and lime green spirals, right? But they are both the same colour! On the right is the same picture with the pink and yellow replaced by black, leaving just one other colour, a fairly ordinary green.

The checkers example of A and B is incredible!

Edited by Iwonderaboutthings

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If " a white piece of typing paper" "did" reveal colors of reds, pinks, blues and orange" "WITH WHITE LIGHT ONLY" and people saw this physically on the white typing paper..

 

WHAT WOULD THAT MEAN???

 

 

If a piece of paper revealed colors with white light only, then the paper isn't white. The color of a physical object is defined by the spectrum of light it reflects.

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So can a black piece.

 

Not exactly, we cannot see infrared. We can see black things because of the absence of all colors.

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If a piece of paper revealed colors with white light only, then the paper isn't white. The color of a physical object is defined by the spectrum of light it reflects.

So then, this may be wrong as I may be able to prove that a plain white piece of paper " does" infact reflect color..

 

"However" light is not entirely placed on the white peace of paper , it seems that the light beams bounce off other objects inside of my room " from the lamp" then "again" bounce off the white peace of paper..

 

I am baffled on this and have never seen anything like this before..

It also appears to be that a "transmission" is being sent IE from the paper due to it revealing color..

Is this wrong to describe like this?

 

 

Perhaps maybe the paper itself, IE recycled paper has something to do with this???

 

The more information I get, the more I will be humbled in sharing how I created this simple experiment, that proves discrepancies with light in general...

 

I also want to ensure that if this is a " true " discovery of mine", that I will have credit and ownership of the find itself and will be added to the list of contributors to science, I may even have a radio interview with a DJ friend of mine to further ground this " maybe" new science discovery by me..

 

It would be nice to work with scientist here as a group and see what else we can find, and simply have fun in doing so..

 

As with all things I discover, I always doubt that perhaps maybe some time long ago someone'else maybe made this discovery and maybe did not really think about sharing this with the world of science or simple did not understand about light and frequencies?? whom knows...

 

 

I would feel very dumb to know that this " paper is showing color" deal was noticed by other artist in their art work too, its confusing!

 

Has anyone here ever heard this before??? I have not and searched for some time now online with no luck.

 

So then, if the paper is not white at all, then what is this??? what is happening then???

 

Like i said I am quite familiar with light, color and frequencies, but this is really " knocking my head off" :blink:

Edited by Iwonderaboutthings

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So then, this may be wrong as I may be able to prove that a plain white piece of paper " does" infact reflect color..

 

 

It will reflect color if the light is colored rather than white.

 

One other other possibility to get colored light is absorption followed by fluorescence. This would be especially noticeable if the light extended into the UV; there are a lot of dyes that fluoresce strongly when exposed to UV light.

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Not exactly, we cannot see infrared. We can see black things because of the absence of all colors.

 

And we see white things "because of the absence of all colours". Black pieces of paper, like white pieces, reflect all wavelengths in the visible spectrum (what we call "light") more or less equally. The difference between black and white is the total amount of light reflected, but our perception of the difference between black and white is relative - a black piece of paper with a white light focused on it will look white, if the surroundings are dark.

 

In other words how light or dark a thing looks is different from what colour it looks - colour depends (partly) on whether some frequencies are reflected more than others, whereas darkness or lightness depends on how much light is reflected.

 

But perception, even of colour, is crucially dependent on contrast. A bright yellow thing can look red, or dark brown, or even black, depending on what is being reflected by its surroundings.

 

And we are "trichromats" - we have three kinds of colour receptors, red, blue and green. That means that we can see non-spectral colours like magenta, if an object reflects both red and blue light, but not green. And yellow light, which stimulates both our red and green receptors (because they are fairly broad-band), gives the same percept ("yellow"), all other things being equal, as objects that reflect no yellow light but pure red and green light, as such objects will also stimulate both red and green receptors.

 

In fact objects that only reflect narrow band "yellow" light will tend to look dingy brown, because they only weakly stimulate red and green receptors, whereas objects that both narrow green and narrow red light (or a white surface on which red and green light is projected) will look bright yellow, both red and green receptors will be strongly stimulated.

 

So "yellow" objects tend to be those absorb blue, and reflect a broad spectrum between green and red, including orange and red, whereas red objects tend to absorb everything shorter than red. Green objects are sort of odd - they have to absorb everything both sides of green, leaving only green reflected. Not surprising, then, that green is very much a "life" colour - probably require something like evolution, or very specific crystalisation processes, to produce. Objects devoid of life tend not to look green!

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I think at this point in the discussion it is important to distinguish between different sensors used to measure the received colour..

 

The human eye will yield a different result from a photoshop colour calibrator, or the calibrator on your scanner.

I think swansont is talking about impartial scientific instruments for measurement.

 

Of course the human eye is connected to the human brain which, as Lizzie says, complicated matters enormously.

 

I bow to her vastly superior knowledge in that human part, which is her particualr area of expertise.

Edited by studiot

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It does complicate matters enormously, but I think it's very important to keep in mind. I've been to lectures on colour (as an architecture student!) where the lecturer though that the three "primary colours" were a fact of the physics of light. They aren't. They are solely a fact of physiology.

 

Personally, I think it's better to think simply about wavelengths, rather than colour, when thinking about the physics of absorption and reflection. Unless we are talking about the colours of living things, which almost certainly evolved because of vision-possessing other living things, and so their physical properties reflect the vision-properties of their predators/seed-eaters/mates, and we are back to vision physiology again.

 

But I should say: I'm not an expert in colour vision! I do have some knowledge though, as it often turns out to be relevant to stuff I do.

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Anyone interested in colours in physics with an interest in the history of science might be interested in Robert Grosseteste's works on Optics, Light, Colours etc. Maybe the dark ages weren't quite so dark and maybe even a little colourful.

 

I was lucky enough to be able to attend this multidisciplinary lecture (a physicist, a historian and a psychologist walk into a bar...) at the Royal Society on Grosseteste and his ideas on colour - it is on video if anyone is interested.

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It does complicate matters enormously, but I think it's very important to keep in mind. I've been to lectures on colour (as an architecture student!) where the lecturer though that the three "primary colours" were a fact of the physics of light. They aren't. They are solely a fact of physiology.

 

Personally, I think it's better to think simply about wavelengths, rather than colour, when thinking about the physics of absorption and reflection. Unless we are talking about the colours of living things, which almost certainly evolved because of vision-possessing other living things, and so their physical properties reflect the vision-properties of their predators/seed-eaters/mates, and we are back to vision physiology again.

 

But I should say: I'm not an expert in colour vision! I do have some knowledge though, as it often turns out to be relevant to stuff I do.

Well Lizzie L, you seem to be quite knowledgeable on color, I have read your comments and wanted to ask if you have ever heard of anyone " seeing" mostly light pastel colors on a white peace of paper, in an atmosphere with mid range dim lighting.

 

The room I saw this in had dim lighting, and I am assuming that bounced light beams from all over the room "somehow" made color appear on this white peace of paper. I even confirmed this with some people I knew personally " HOWEVER"

 

The only way you could see the colors is if you focus your attention on a section of this white paper, and after a few seconds, the colors start to form on the paper itself....Surly their has been someone out there whom has stumbled on this too?

 

 

The colors are light reds, light oranges, and blues...

 

It will reflect color if the light is colored rather than white.

 

One other other possibility to get colored light is absorption followed by fluorescence. This would be especially noticeable if the light extended into the UV; there are a lot of dyes that fluoresce strongly when exposed to UV light.

Hymm not at all with UV light, the other day, I tried the technique with plain sun light without a light bulb and I saw colors on the white peace of paper...I need to mention that I used a blanket to cover the window to make the room dim and not so bright trying to balance light at 1/2 its normal brightness in my room, would that be a reason for seeing colors on the white peace of paper??

 

If this was a legitimate find and the science community was interested in this further, would there be anyway to get this peace of paper inspected on how light reflects off the surface " with my guidance"?

Edited by Iwonderaboutthings

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