This page is an archive of past discussions. Do not edit the contents of this page. If you wish to start a new discussion or revive an old one, please do so on the current talk page. |
optical spectrum from radio to x-rays? where did you get that from? please, references.
--[[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)
--[[User:Dkroll2| Dkroll2]] 06:32, Dec 19, 2004 (UTC)
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
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)
hacker got me 66.245.87.206 21:11, 15 Dec 2004 (UTC)
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?
Oxford English Dictionary: spectrum 2nd Ed. 1989 Caltrop 13:08, Mar 5, 2005 (UTC)
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)
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)
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:
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)
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)
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)
Is it a coincidence that the visible spectrum is approximately one octave? —Ben FrantzDale 22:02, 28 April 2006 (UTC)
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. –M T 00:49, 5 June 2006 (UTC)
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.
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)
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.
sorry, reverted-my mistake
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)
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)
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)
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.
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
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)
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)
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)
...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.
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)
The comment(s) below were originally left at Talk:Visible spectrum/Comments, and are posted here for posterity. Following several discussions in past years, these subpages are now deprecated. The comments may be irrelevant or outdated; if so, please feel free to remove this section.
In WP Physics |
Last edited at 19:43, 26 August 2006 (UTC). Substituted at 16:04, 1 May 2016 (UTC)
This page is an archive of past discussions. Do not edit the contents of this page. If you wish to start a new discussion or revive an old one, please do so on the current talk page. |
optical spectrum from radio to x-rays? where did you get that from? please, references.
--[[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)
--[[User:Dkroll2| Dkroll2]] 06:32, Dec 19, 2004 (UTC)
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
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)
hacker got me 66.245.87.206 21:11, 15 Dec 2004 (UTC)
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?
Oxford English Dictionary: spectrum 2nd Ed. 1989 Caltrop 13:08, Mar 5, 2005 (UTC)
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)
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)
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:
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)
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)
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)
Is it a coincidence that the visible spectrum is approximately one octave? —Ben FrantzDale 22:02, 28 April 2006 (UTC)
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. –M T 00:49, 5 June 2006 (UTC)
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.
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)
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.
sorry, reverted-my mistake
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)
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)
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)
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.
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
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)
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)
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)
...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.
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)
The comment(s) below were originally left at Talk:Visible spectrum/Comments, and are posted here for posterity. Following several discussions in past years, these subpages are now deprecated. The comments may be irrelevant or outdated; if so, please feel free to remove this section.
In WP Physics |
Last edited at 19:43, 26 August 2006 (UTC). Substituted at 16:04, 1 May 2016 (UTC)