Talk:Visible spectrum

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optical spectrum from radio to x-rays? where did you get that from? please, references.

I find it strange too, but it's lifted verbatim from the Federal Standard 1037C. I'm in doubt about removing the paragraph or not. At18 19:18, 16 Aug 2003 (UTC)
At18 21:19, 16 Aug 2003 (UTC) Following be bold in updating pages policy, I removed this paragraph (radio? X-rays????):
The term "optical spectrum" originally applied only to that region of the electromagnetic spectrum which is visible to the normal human eye, but is now considered to include all wavelengths between the shortest wavelengths of X-rays and the longest of radio. At this writing, no formal spectral limits are recognized nationally or internationally.

--[[User:Dkroll2|Dkroll2]] 19:07, Dec 14, 2004 (UTC) Optical means optics, which means visible. Wwll actualy I DID fin the reference to optical spectrum from radio t x-rays. now I lost it, but he was right --[[User:Dkroll2|Dkroll2]] 05:49, Dec 19, 2004 (UTC)

check out this definition exteral
http://www.atis.org/tg2k/_optical_spectrum.html

--[[User:Dkroll2|Dkroll2]] 06:32, Dec 19, 2004 (UTC)

Contents

[edit] Image of the visible spectrum

Why isn't there a picture of the visible spectrum here? Malbi 13:35, 2 Dec 2003 (UTC) There is now --[[User:Dkroll2|Dkroll2]] 19:07, Dec 14, 2004 (UTC)

Still agrument further down ar to how it should appear. It is burned in my brain. Theonly thing I could do is to add absorption line (too much info for this page) pr make the cy light/brighter, but NOT wider. It isn't any wider.--[[User:Dkroll2|Dkroll2]] 07:47, Dec 19, 2004 (UTC)

  Can I make a suggestion people?
  Add frequency and/or wavelength ranges to the image... As in the approximate fequency/wavelength of each colour as a regular scale on the bottom of the image. -Prince.Buster


May I ask a question? How do you think the "visible light spectrum image" should be orientated? -Peter

[edit] Some more info...

This text below is what I used already in a presentation of mine (the electromagnetic spectrum). I wanted to include more and happened to land here. Besides "taking", I'd figure I'd "give" something too. Don't know whether this is usefull or not for inclusion, but here it is:

Visible spectrum is only a very small band of the EM spectrum, though it is emitted and reflected by almost everything and it is also least absorbed by the atmopshere. Probably this is why evolution decided to make the four cells in the retina of the human eye sensitive to it. One type of cell 'feels' the intensity of light, the other 3 covers Redish, Greenish and Blue-ish intensities (each with it's sensitivity curves). Hence we can see all colours by a combination of those 3. --[[User:Dkroll2|Dkroll2]] 19:07, Dec 14, 2004 (UTC) I wrote the same thing in simler language NO, not really.

use: fibre optics, Astronomy use: RGB (red green blue) in TV / computers to "fool" our eyes to see all visible colors by adding different saturations of these colors use: CYV (Cyan Yellow Violet?) in printers / copiers /painters to do the same thing but by substracting values

Cheers, e-builds


Can't recall for certain where I picked this up... Could have been in a Physics lecture. I'm given to understand that the various colors detected by the eye are not of fixed width -- that is, the wavelengths perceived as green may be a wider band than those perceived as blue. Each person may have a slightly different 'eye' for colors also.

See: Trichromat, Tetrachromat.

karlheg 01:35, 2004 Oct 29 (UTC)

[edit] Include vs. exclude cyan

hacker got me 66.245.87.206 21:11, 15 Dec 2004 (UTC)

[edit] No, my intention is never to neglect cyan

I stare at spectrums all day. And how ,say the sky, appears at first glance is RED GREEN BLUE, then you will next notice the narrow region of yellow, then next too it a small amout of orange, then you might notice a very thin region of cyan, then you see the violet. I've watched hundered of student go thourough this same exercise will all continuous sources. Personally as I review my diagram, I may have too much cyan as compared to what is witnessed from the sun. HOWEVER I might attempt to make it lighter, as both yellow and cyan shoud be the lightest hues since they excite 2 sets of cones.

What should I do?--[[User:Dkroll2|Dkroll2]] 05:58, Dec 19, 2004 (UTC) Is this what more scientists are used to sho have never actually view the light of the sun througha simple prism?

[edit] I'm deleting my stuff on this page. A hacker screwed me over.

--[[User:Dkroll2|Dkroll2]] 13:22, Dec 24, 2004 (UTC)

[edit] Source for Newton date 1671

Oxford English Dictionary: spectrum 2nd Ed. 1989 Caltrop 13:08, Mar 5, 2005 (UTC)

[edit] what is this "compound phenomenon" stuff?

What is this section on "compound phenomenon"? In particular, who is this Goethe that keeps getting mentioned, why are his views on the color spectrum notable, and how do they relate to other views? Is this the 18th/19th century Johann Wolfgang von Goethe we're talking about? --Delirium 04:19, May 31, 2005 (UTC)

I have been bold and removed that section. I do not think these (presumably) 200 year old theories are relevant, and they were presented in a way which made them sound like an alternative to the modern understanding of what a spectrum is. They may warrant a paragraph in a history of spectroscopy article, but don't merit inclusion here, I don't think. Worldtraveller 1 July 2005 09:58 (UTC)

Actually it is the same Goethe, which is why he's mentioned by his last name...the rest is usually assumed due to his notoriety. As for not including his theories (seen also in the Theory of Colors entry), his theories are apparently considered relevant enough to be still included in at least two college textbooks I'm aware of, Contemporary Color: Theory and Use by Steven Bleicher, and Color by Mary Pat Fisher and Paul Zelansky. They are as relevant as any equally noteworthy historical record of the theories espoused on color, since they are, after all, theories and not irrefutable scientific fact: we still don't quite comphrehend a lot about (or have only recently discovered) why many of the functions of the eye work the way they do, and there are some, such as Munsell, who dispute the popularly held notion of a traditional 3-color primary based color wheel altogether. Dain Quentin Gore 05:57, 17 August 2006 (UTC)

[edit] Definition

The current definition reads: "The optical spectrum (light or visible spectrum) is the portion of the electromagnetic spectrum that is visible to the human eye." I suggest removing "human", but there seems to be some objection. Although "optical spectrum" and "visible spectrum" are most often used in the context of discussing human physiology, they are not defined by human physiology. Perhaps those in favor of keeping "human" could answer a few questions that this article should answer:

  1. As used here, here, and here, is the term "human visible spectrum" redundant?
  2. As used here is the term "canine visible spectrum" an inappropriate combination of terms?
  3. If "human" stays, what is the name for the portion of the electromagnetic spectrum that other species can see?
  4. If "human" stays, then this article defines "light" as "the portion of the electromagnetic spectrum visible to the human eye". Is light not visible to other species that are not human? --Edwardian 20:32, 23 September 2005 (UTC)

But they are defined by human physiology. The term 'visible' is meaningless without specifying what the detector is, and on its own it implicitly means 'visible to humans'. As your links show, different species have very different spectral responses. Clearly, the canine-visible spectrum is one term which can be used to describe the wavelengths which a dog's eye perceives. If light is defined as EM radiation that human eyes can perceive, it does not follow at all that non-humans can't perceive it, so I see no problems with the definition as it currently stands. Worldtraveller 00:19, 24 September 2005 (UTC)

If "visible" is meaningless without specifying what the detector is, then how can you just assume that the detector is human and assert that it implicitly means "visible to humans"? (As you suggest, we can talk about what is visible to other species, too.) What is the term for the "very different spectral responses" that different species have? And how do you define the "canine-visible spectrum"? And if "light" is defined as "EM radiation that human eyes can perceive" (which is not the definition in the article Light), then what is the name for the "EM radiation that other species can perceive"? Edwardian 04:50, 24 September 2005 (UTC)

I'm not sure what you're arguing for here. If you want to define visible light as EM radiation that is visible to any eye, then that would make infrared and ultraviolet radiation visible light, which doesn't make any sense. The EM radiation that other species can perceive may be light, as we know it, or it may also include IR, UV or whatever. I don't see what your problem is with that. Worldtraveller 15:13, 24 September 2005 (UTC)

We agree that what is visible to one species is not necessary visible to another species. That is, each species has its own visible spectrum. What I am arguing is that by defining it merely as that which is visible to humans, this article actually ignores that each species has its own visible spectrum.
The eye is not defined as the organ that detects light in humans. The reason is that definitions are supposed to reflect the essential properties of a concept and “in humans” is not an essential property of the concept “eye” because other species have eyes. Similarly, “to the human eye” is not an essential property of the concept “visible spectrum” because other species have visible spectra. Edwardian 22:00, 24 September 2005 (UTC)
Well, I think the optical/visible spectrum is the one that (most) humans see (ignoring issues like colour blindness, etc). I'm sure that is the one that Isaac Newton would have been thinking of. But perhaps we need another sentence in the lead section along the following lines:
"The eyes of many species can perceive wavelengths outside the spectrum visible to the human eye. For example, many insects, such as bees, can see light in the ultraviolet, which is useful for finding nectar in flowers, and [example] can see light in the infrared, [because]. "
Would this satisfy you? -- ALoan (Talk) 09:07, 25 September 2005 (UTC)
I agree that "the visible spectrum" is most commonly used in the context of what humans can see. I would argue that because it is not always used in the context of what humans can see, "to the human eye" should be left out. Still, because it is usually used in the context of what humans can see, perhaps your suggestion is the better one for serving the practical purposes of an encyclopedia. Cheers! Edwardian 18:48, 25 September 2005 (UTC)
I implemented the above suggestion, but changed "outside" to "different than". Edwardian 05:17, 27 September 2005 (UTC)

Without question, the "optical spectrum" includes the "human visible spectrum" as a subset, but they are not synonymous phrases. The infrared and UV spectra are both optical (which, I think, is synomymous with "electromagnetic radiation"), but neither are perceptible by humans. If you are going to use "visible", it is necessary to specify "humans" as part of the definition. Some animals have very good IR capability, and some (certain types of hawk come to mind) have some UV capability. I think it is worthwhile to state at the top that for the remainder of the article, unless otherwise specified, "visible" implies "visible to humans", and specifically, photopic (as opposed to scotopic). Ehusman 15:17, 18 December 2005 (UTC)

I would define light as the electrodynamical wave's frequency spectrum that the eye's receptors react on as frequency-depending colours. This implies that the light-spectrum is relative to the observers motion. With the observer's increasing velocity towards the source of the radiation that moves in the absolute space with velocities related to the wavelengths, the observer's colour spectrum changes proportional to longer wavelengths (and vice versa in the other direction). The reason to this is that the eye's frequency-spectrum is invariant. In that meaning light is a physiological reaction on physical radiation of a specific frequency-spectrum. This explanation implies that Einstein's speculations about the Lorentz transformation interpretation are false and the consequences are that there are no change of time or space with increasing velocities. IngvarA 19:27, 12 January 2006 (UTC)

[edit] Octave?

Is it a coincidence that the visible spectrum is approximately one octave? —Ben FrantzDale 22:02, 28 April 2006 (UTC)

Probably. It's not a coincidence that it spans a region where water vapour has low absorption.--Srleffler 23:35, 28 April 2006 (UTC)

[edit] Health effects

If there has been any research showing that the actual spectrum of flourescent light is harmful, there should be some references in the text to some relevant sources. I have heard, and have easier to believe, that the flicker of some flourescent lights can cause headache, but not the spectrum. europrobe 19:10, 16 May 2006 (UTC)

What I've read of the over-illumination article states that light being too bright is the cause. White light is brighter than, say, yellowish light, yes, but we should be careful about implying that certain specra are harmful (as if looking at blue light is better or worse for your health than looking at purple light). Quite a few sources would be needed to back up such a claim. Removed section included below. –MT 00:49, 5 June 2006 (UTC)

This is a major problem with the over-illumination article, that it mixes together the idea of light being too bright with issues of the health merits of natural vs. artificial illumination. It's actually perhaps more likely that the health impacts discussed there, if real, are caused by the spectrum of the light rather than the intensity being too high. On a typical day, sunlight is between thirty and a hundred times more intense than the levels of illumination found in an "over-lit" office. The claim that excessively bright artificial lighting can cause health impacts because it is too bright would be quite extraordinary, and would require extraordinary evidence to support it.--Srleffler 05:01, 5 June 2006 (UTC)

[edit] Health implications of artificial spectra

 This section does not cite any references or sources. (December 2006)
Please help improve this section by adding citations to reliable sources. Unverifiable material may be challenged and removed.

When humans are exposed to spectra different from natural light, certain health implications may arise. Research on effects of fluorescent light have particularly shown increased incidence of headache, fatigue and stress, especially with exposures of several hours duration; moreover, the pineal gland and circadian rhythm may be altered in function by exposure to fluorescent or other lighting systems differing in spectra from sunlight.

See also: Over-illumination

[edit] Clever advertisement? not sure

At the top it says:

"Visible Light" redirects here. For science fiction book, see The Collected Short Fiction of C. J. Cherryh.

Is there a particular reason why that is at the top? Seems like advertisement to me, cleverly inserted to be overlooked.

Bleedstupid 17:25, 14 August 2006 (UTC)

It's so people looking for the book "Visible Light" can find the proper article. "The Collected Short..." contains material which had been in the "Visible Light" book. (SEWilco 18:49, 14 August 2006 (UTC))
Quite legit under Wikipedia:Disambiguation, though not a very important meaning. I made it less conspicuous by replacing it with a generic disambiguation page. Femto 18:55, 14 August 2006 (UTC)
Do not create disambiguation pages that have only two entries. Per Wikipedia:Disambiguation#Top links, this case is covered with a disambiguation link at the top of both of the articles, rather than a disambiguation page. The article was perfectly correct as it was.--Srleffler 00:58, 15 August 2006 (UTC)
It's not a mutual disambiguation case, visible spectrum does not redirect to visible light. I did check if two-entry redirects are covered, but WP:D only tells to put a topnote to the "topic's disambiguation page", which I did. It just seems wrong that any minor topic could impose its name on a main topic just because there are no other disambiguations. What if there was a truly commercial "Visible Light" corporation (and no book), should they get a prominent adlink at the top of this page too? Femto 12:43, 15 August 2006 (UTC)
You missed it. Scroll down to the section WP:D#Top links, where it says "If there are a pair of articles which ought to be disambiguated from each other, include a link to the "opposite" page in each." (emphasis mine). They give examples too. The instructions are unambiguous: when there are only two pages, their toplinks link to each other and not to a disambig page. Yes, indeed if there were a "Visible Light Corporation" that was notable and otherwise merited a Wikipedia article, it would be entirely appropriate to have an otheruses link to it at the top of the article (assuming there were no other meanings). If the corporation merits an article here, it's not advertisement to link a relevant term to that article, in the same way that the article itself is not an advertisement. If you want to see an example comparable to the current article, check the dablink at the top of optics. Just like in this case, we have a much more minor article being linked from a very important article, and it's due to a redirected term, not even the title of the article itself.--Srleffler 02:39, 16 August 2006 (UTC)
These are not a pair of articles with ambiguous names. The Collected Short Fiction of C. J. Cherryh does not need to be disambiguated from visible spectrum, the instructions on mutual disambiguation don't apply here. If not an advertisement, a specific topnote to a very minor topic still constitutes undue visibility. I find that a lot more disturbing than a two-entry dabpage. Femto 13:01, 16 August 2006 (UTC)
I think the disambiguation page is a better solution at the moment. Many readers will approach this article through various spectrum-oriented topics, and "visible light" is a more general term. The disambiguation page makes clear to "visible light" readers that the topic is presently covered in this article. On another solution, I think the Cherryh link does not fit well in "See also" of this spectrum article. I recognize someone might write a suitable "visible light" article, but that is a different situation than this situation which involves a redirect. I think the Cherryh page does not require a disambig link here. (SEWilco 21:30, 16 August 2006 (UTC))

[edit] Brown and Pink do exist!

I deleted the last sentance of the first paragraph that stated, "The spectrum does not, however, contain all the colors that the human eyes and brain can distinguish. Brown and pink are absent, for example. See Color to understand why." It's misleading to say that brown and pink are not included, as they most certainly are. They are varying intensities of colors (orange and red, respectively). The deleted sentance seemed to imply that our brains invented brown and pink.

Pink is not in the spectrum in the same sense as white is not in the spectrum--it is a combination of three primary colors. You could see pink as a combination of red and white, or as a combination of red, green, and blue with a little excess of red. Itub 22:38, 16 August 2006 (UTC)
No one is saying brown and pink don't exist. They just aren't in the spectrum. Ordinary Person 02:28, 17 August 2006 (UTC)
If you use a prism to split a pink or brown light into a spectrum I think you'll find a few bright bands, rather than a single band of color. The human eye can interpret combinations of color, and not all colors are created by the prism process because it separates colors. However, "visible spectrum" refers to all colors in the "visible light" range and not only the rainbow color pattern. I do note that there are several color combination displays, such as an RGB color wheel. (SEWilco 03:50, 17 August 2006 (UTC))
If you try to use a prism to split brown light into a spectrum you will fail, because there is no such thing as brown light. It doesn't exist. Really. If you take a slide projector and project a picture of a tree on a screen in a dark room the trunk will look brown. If you then add an aperture that allows you to restrict the displayed scene to just a small portion of the treetrunk, the light will appear orange because it is orange. It only looks brown when it is juxtaposed with other colors in the scene. Visible spectrum refers to the actual electromagnetic spectrum of light in the visible range. As you noted, the eye can interpret combinations of spectral colors as other colors, even ones that are not present in the light at all. In addition though the eye and brain create colors that are not part of the spectrum; there is no such thing as light of that color.--Srleffler 03:59, 17 August 2006 (UTC)
But the page still says that pink and brown require multiple frequencies of light. This is certainly true for pink, but for brown, it's misleading (and probably false). Brown can be produced as a shade of yellow to red light, and you only need contrast to produce it. Is it really true that you can't produce brown with a single frequency? (say, an orange bright monochromatic background surrounding a darker swatch?) 75.130.108.174 (talk) 22:43, 10 May 2008 (UTC)
Actually, our brains do invent brown and pink, and many other colors. Color is primarily a creation of the human mind. It is related to the spectrum of light, but it's not a direct one-to-one relationship. Color perception is very complex. Our eyes perceive independent spectral colors as "mixing" to produce other colors. This is completely an artifact of the brain. Also, the color that things appear can depend on the color of other objects in the scene. For example, you can't make a brown spotlight. Brown only exists when a dark, low-saturation orange or red is juxtaposed with brighter colors. If you try to make a brown spotlight and light a dark space with it, you only get orange.--Srleffler 03:54, 17 August 2006 (UTC)
Yes, it's like how we interpret some molecules as tasting "sweet". The original, a light or chemical, just activates our senses in a way which is interpreted as "pink" or "sweet". Once someone tells us the name for that color or taste we can use that word for it. Shades of brown is convenient for interpreting our environment, just as are variations of sweetness. (SEWilco 05:18, 19 August 2006 (UTC))

[edit] Visible spectrum is not in nm, but in um region !

sorry, reverted-my mistake

[edit] Capitalization

It wasn't necessary to revert my de-capitalization of links to other articles. The capitalisation section of Wikipedia:Manual of Style (links) says that both styles are allowed. I won't start an edit war; if you prefer links to be capitalized, I'll leave it like that. I find that Wikipedia articles tend to look like they're written in German with words being capitalized for no reason, and have been actively trying to fix that. Julesd 13:46, 28 January 2007 (UTC)

[edit] red light moving more quickly in glass than violet light?

isn't the difference of frequencies of the waves that results different refractive indices, thus red light was bent (refracted) less sharply than violet light as it passed through the prism, creating a spectrum of colors?? Nichehole 09:30, 17 April 2007 (UTC)

[edit] The visible spectrum colors are displayed in reverse order

Compared with the traditional order of displaying the visible spectrum, the colors of the graphic on this page are shown in *reversed order* with ultraviolet on the left and red on the right. The visible spectrum is traditionally represented from left to right as red to ultraviolet, respectively. Thus the traditional order displays the frequency and energy scales *increasing* from low to high from left to right and, perhaps counterintuitively, shows the wavelengths *decreasing* from left to right.

Perhaps a contributing confusion factor is that the colors of the chromatic dispersion of white light after passing through an appropriate prism are reversed with the slowest frequency (red) appearing at the top. The colors of an ordinary rainbow also appear in reversed order, i.e., from red (longest wavelength, lowest energy, slowest frequency) at the top to ultraviolet (shortest wavelength, highest energy, fastest frequency) at the bottom.

67.142.130.13 19:32, 10 June 2007 (UTC)

[edit] Seeing Infrared?

From the first paragraph: "some people may be able to perceive wavelengths from 380 to 780 nm[citation needed]." This implies some humans can see in Infrared, which begins with 750 nm, according to the section at the bottom of the article, "Spectral Colors", and the article on infrared. So my question, which I raise because, since it lacks citation as specified, is: Is this true? Because it is contrary to the article on infrared, and everything I've ever been told about visible light.

[edit] Sophists?

Newton may have believed that the Sophists reasoned that seven days of the week and seven planets implied seven colors, but what was Newton's source? I ask because this sort of reasoning is radically out of character with Plato's description of Sophists as being "on the side of the Earth Giants."

A "seven days implies seven planets" argument had been used against Galileo, but this is a "side of the Gods" argument, i.e., it implies that a necessary and certain knowledge of reality can be logically deduced. It was Plato's "Socrates" who claimed that knowlege could be necessary and certain, while Plato's "sophists" claimed that knowlege was merely unquestioned opinion.

70.187.212.62 12:21, 1 September 2007 (UTC) Dan Holdgreiwe

[edit] Violet - a myth that we are perpetuating here.

Hi!

I've just been embroiled in a long debate over on the Wikipedia science reference desk about the colour 'violet'.

It is well known that the human eye sees only three primaries, red, green and blue - red being low frequency light, blue being highest and green being somewhere between the two. Three separate sets of colour sensors - each with a roughly gaussian frequency response.

Why then does the 'spectrum' image at the top of the page show magenta light off to the left of the blue? In reality, as the frequency of light increases, you see first red, then yellow (because pure yellow light stimulates both red and green sensors), then green, then cyan (which stimulates both green and blue sensors), then blue - as the frequency of the light increases above blue, our blue sensor gets less and less sensitive - so the colour fades out to black. How could there possibly be any red stimulation at such a high frequency? The answer is, there isn't any. It's a complete myth that there is a patch of "violet" light at the higher frequency end of the band. (The term "ultra-violet" is a misnomer brought about by this myth - it ought to be called 'ultra-blue').

The reason the myth comes about is because most people's common perception of white light spread out into a spectrum is in a rainbow. Most of the time, there is no 'violet' light in a rainbow - but sometimes (rarely) you get so-called 'supernumerary rainbows' where (due to some complicated thing relating to raindrop geometry) you get multiple rainbows that overlap very slightly. In this cases, the red light from one rainbow overlaps the blue of another and you see magenta ('violet') light. However, if you look at a simple, clean spectrum from (say) a triangular glass prism - there is no violet light (which is what you'd expect from examination of the way the human eye sees colour).

We need to (a) fix the image to remove the violet and (b) explain what's really going on here.

SteveBaker 17:31, 25 September 2007 (UTC)

There must be a violet, by hook or crook, in order for there to be seven colors in Newton's "spectrum." Look in Newton's Opticks, Book I, Part II, Proposition III, Problem I. There, he claimed that a spectrum's colors are in the "ratios of certain musical chords." In Book II, Part II, Proposition XVI, he asserted that the rays of light were like the "lengths of a chord which found the notes in an eighth, sol, la, fa, sol, la, mi, fa, sol ". Newton's "spectrum" is something like the sound of music: "a needle pulling thread; a note to follow sol; a long, long way to run; a name I call myself;" etc.Lestrade 17:55, 25 September 2007 (UTC)Lestrade
SteveBaker: Your color theory is off. Red, green, and blue are considered primary colors of light generally, but it's well known that this is only part of the story; in particular, as the canonical example, the very colors you are claiming don't exist tend to produce saturations of "reddish violets" that your average RGB monitor is incapable of creating (i.e., with just red, green, and blue, you can only reproduce the sensation of a shade or more impure version of these colors).
Our S,M,L cones also don't work like your R,G,B monitors; L and M sensitivities are much closer to each other at peak than red is to green (the peak sensitivity for L, for example, is ~560nm). It's not the outputs of the L cone that we see as red, but rather, the difference between L and M (L-M). M sensitivity falls off at the longer wavelengths more than L, resulting in a larger difference, and thus more red sensation. The same is true, however, at the opposite end of the spectrum--M falls off, again, sharper than L. This also triggers a red response, which works in concert with the blue response producing a violet. Some of this is documented in the wiki article on opponent process.
75.130.108.174 (talk) 22:43, 10 May 2008 (UTC)

Colour Side Effects

Often exposior to too much light can cause unpleasant deseases like skin cancer. THis can be avoided by wearing enough sun screen and not spending too much time in the sun. Recent studies show that sunbathing near glass increases suhn rays by 200 procent. —Preceding unsigned comment added by 217.140.78.70 (talk) 12:06, 17 October 2007 (UTC)

[edit] ROYGBIV

How about mentioning ROYGBIV stuff we learn in Grade school? (Red, Orange, Yellow, Green, Blue, Indigo, Violet) —Preceding unsigned comment added by 24.87.84.158 (talk) 06:40, 15 November 2007 (UTC)

It's already mentioned in plenty of places in wikipedia. Dicklyon 06:44, 15 November 2007 (UTC)
Then I think it makes sense to do it here, too -- so I did. Travisl (talk) 01:09, 26 January 2008 (UTC)

[edit] It is generally accepted...

...that light is composed of photons? I apologize for not reading the entire edit history, I generally stick to the pages that I have been keeping track of, but non-scientists often don't get that when we say "generally accepted" we don't mean "maybe", we mean, "We'll assume you're not credible if you say otherwise." As Wikipedia is an encyclopedia intended for everyone, we should use words they understand...light is composed of photons.

But the photon is only the particle half of the wave–particle duality view of what light is. It would just as correct (and just as wrong) to say that light is made up of electromagnetic waves. I agree that "it is generally agreed" is probably just a WP:WEASEL word way to avoid the issue, so maybe we should work on a better way. I don't think it's right to say that photons have wave propreties; they are the particle half of the picture, which make sense for how light interacts with matter, but not so useful for how light propagates. Dicklyon (talk) 01:13, 24 December 2007 (UTC)
Different interpretations of quantum mechanics will approach this issue differently. For example, in Mead's approach, similar to the transactional interpretation, a photon is an epiphenomenon of the interaction of electron wave functions. See this page of his book to get an idea about what he thinks a photon is. Probably it would be a good idea to avoid the issue in this article, since photons don't have much to do with the electromagnetic spectrum, visible or otherwise; the spectrum is a wave-only interpretation of light. Dicklyon (talk) 01:41, 24 December 2007 (UTC)

[edit] Another little problem

I took out the distracting photon bit as it added nothing relevant to the spectrum discussion. But in the process I noticed "In some materials, known as non-dispersive...". And here I have a problem. Do such materials exist? I don't think so, unless you count vacuum as a material. It's a decent pedagogical approach, but we shouldn't pretend they exist if they don't. Dicklyon (talk) 01:54, 24 December 2007 (UTC)

Deleting "photons" was a nice solution, thanks. More than half of the American public thinks that there's no compelling evidence for natural selection, and we as scientists are in a small way responsible for the common belief that we're not sure about anything we say, if we say "it is generally accepted" when we mean "it's difficult to explain." — Dan Dank55 (talk) 02:16, 24 December 2007 (UTC)
I think "non-dispersive material" is only used as a model in idealized situations, to simplify solving problems where dispersion is low enough to ignore. So it's indeed misleading to suggest that such materials exist in the physical world. --jacobolus (t) 10:27, 24 December 2007 (UTC)

[edit] Audible spectrum

Is there any article on Audible spectrum?Anwar (talk) 19:35, 3 May 2008 (UTC)

[edit] The actual range of the spectrum

Isn't the exact range of the visible spectrum disputed?--Luke Elms 20:33, 17 May 2008 (UTC)

Not that I know of. It is widely accepted that there is no "exact range", since the sensivities curves fall gradually to zero at both ends. Dicklyon (talk) 21:33, 17 May 2008 (UTC)