# What is "Pink" light? Can it be monochromatic? **URL:** \ **Category:** Factual Questions\ **Created:** [August 27, 2013, 12:42am UTC](https://boards.straightdope.com/t/what-is-pink-light-can-it-be-monochromatic/667264 "2013-08-27T00:42:57Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Trinopus](https://avatars.discourse-cdn.com/v4/letter/t/2bfe46/32.png) [@Trinopus](https://boards.straightdope.com/u/Trinopus)\ **Post date:** [August 27, 2013, 12:42am UTC](https://boards.straightdope.com/t/what-is-pink-light-can-it-be-monochromatic/667264/1 "2013-08-27T00:42:57Z")
Does the term “monochromatic pink light” make sense? Could someone invent a “pink” laser? My guess is, no. Pink doesn’t exist on the spectrum. So, then, if you shine white light through a pink transparency, what’s coming through? A mixture of red and white? An ordinary white spectrum, but with an artificial bulge or spike in the red region? Or is there no such thing at all as “pink” light, even as a blend of light spectrum curves? (Can you mix light spectrum curves?) Not a homework question. (Ideas for a story I might write some day…) ---
**Author:** ![Amateur\_Barbarian](https://avatars.discourse-cdn.com/v4/letter/a/59ef9b/32.png) [@Amateur\_Barbarian](https://boards.straightdope.com/u/Amateur_Barbarian)\ **Post date:** [August 27, 2013, 1:30am UTC](https://boards.straightdope.com/t/what-is-pink-light-can-it-be-monochromatic/667264/2 "2013-08-27T01:30:08Z")
Sounds like someone read about white noise and pink noise and decided white light needed a companion. ---
**Author:** ![Gary\_Robson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gary_robson/32/3448_2.png) [@Gary\_Robson](https://boards.straightdope.com/u/Gary_Robson)\ **Post date:** [August 27, 2013, 1:31am UTC](https://boards.straightdope.com/t/what-is-pink-light-can-it-be-monochromatic/667264/3 "2013-08-27T01:31:21Z")
I think **Amateur Barbarian** nailed it. > [@Trinopus](#): > > An ordinary white spectrum, but with an artificial bulge or spike in the red region? That’s what I’d call “pink light.” ---
**Author:** ![Trinopus](https://avatars.discourse-cdn.com/v4/letter/t/2bfe46/32.png) [@Trinopus](https://boards.straightdope.com/u/Trinopus)\ **Post date:** [August 27, 2013, 1:37am UTC](https://boards.straightdope.com/t/what-is-pink-light-can-it-be-monochromatic/667264/4 "2013-08-27T01:37:06Z")
Actually, I remember Martin Gardner’s “Mathematical Games” column on pink noise and brown noise. Interesting stuff, but within my comprehension. Optics, maybe not so much. (I always get caught up in the distinction between “light” colors and “paint” colors.) Anyway, was my guess right and there could not be a “pink” laser? (I mean, other than having it shift frequencies really rapidly, but then it isn’t monochromatic any longer…) ---
**Author:** ![Belowjob2.0](https://avatars.discourse-cdn.com/v4/letter/b/b9e5f3/32.png) [@Belowjob2.0](https://boards.straightdope.com/u/Belowjob2.0)\ **Post date:** [August 27, 2013, 1:41am UTC](https://boards.straightdope.com/t/what-is-pink-light-can-it-be-monochromatic/667264/5 "2013-08-27T01:41:53Z")
[http://www.newscientist.com/blogs/nstv/2011/10/one-minute-physics-why-there-is-no-pink-light.html](http://www.newscientist.com/blogs/nstv/2011/10/one-minute-physics-why-there-is-no-pink-light.html) Yup. ---
**Author:** ![Ike\_Witt](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ike_witt/32/283_2.png) [@Ike\_Witt](https://boards.straightdope.com/u/Ike_Witt)\ **Post date:** [August 27, 2013, 1:42am UTC](https://boards.straightdope.com/t/what-is-pink-light-can-it-be-monochromatic/667264/6 "2013-08-27T01:42:50Z")
You should read [VALIS](http://en.wikipedia.org/wiki/VALIS). ---
**Author:** ![thelurkinghorror](https://avatars.discourse-cdn.com/v4/letter/t/7c8e57/32.png) [@thelurkinghorror](https://boards.straightdope.com/u/thelurkinghorror)\ **Post date:** [August 27, 2013, 2:57am UTC](https://boards.straightdope.com/t/what-is-pink-light-can-it-be-monochromatic/667264/7 "2013-08-27T02:57:27Z")
> [@Trinopus](#): > > So, then, if you shine white light through a pink transparency, what’s coming through? A mixture of red and white? An ordinary white spectrum, but with an artificial bulge or spike in the red region? Depends on what you’re using to make the light. Only very specialized devices can make a flat spectrum. Other times, you have to rely on a metamer that appears white. For example, many of the [standard illuminants](http://en.wikipedia.org/wiki/Standard_illuminant) (see figures) might all appear white to us, but certainly aren’t spectrally. ETA: But on rereading, a transparency does not create light, but filters out certain regions. If it is truly pink, then wavelengths (middle part?) will be attenuated. ---
**Author:** ![Trinopus](https://avatars.discourse-cdn.com/v4/letter/t/2bfe46/32.png) [@Trinopus](https://boards.straightdope.com/u/Trinopus)\ **Post date:** [August 27, 2013, 3:07am UTC](https://boards.straightdope.com/t/what-is-pink-light-can-it-be-monochromatic/667264/8 "2013-08-27T03:07:43Z")
> [@Belowjob2.0](#): > > [http://www.newscientist.com/blogs/nstv/2011/10/one-minute-physics-why-there-is-no-pink-light.html](http://www.newscientist.com/blogs/nstv/2011/10/one-minute-physics-why-there-is-no-pink-light.html) . . . Yup. Cool! That was fun! I’ll refer to it as “minus green” from here on! > [@Ike\_Witt](#): > > You should read [VALIS](http://en.wikipedia.org/wiki/VALIS). Well, okay. It’s one I haven’t read before, and what Dick I have read, I’ve liked. So, deal! > [@thelurkinghorror](#): > > Depends on what you’re using to make the light. Only very specialized devices can make a flat spectrum. Other times, you have to rely on a metamer that appears white. For example, many of the [standard illuminants](http://en.wikipedia.org/wiki/Standard_illuminant) (see figures) might all appear white to us, but certainly aren’t spectrally. > > ETA: But on rereading, a transparency does not create light, but filters out certain regions. If it is truly pink, then wavelengths (middle part?) will be attenuated. Like the “minus green” in the video? Thank you, all y’all! ---
**Author:** ![njtt](https://avatars.discourse-cdn.com/v4/letter/n/ecd19e/32.png) [@njtt](https://boards.straightdope.com/u/njtt)\ **Post date:** [August 27, 2013, 3:42am UTC](https://boards.straightdope.com/t/what-is-pink-light-can-it-be-monochromatic/667264/9 "2013-08-27T03:42:42Z")
Next problem: brown light. 😛 ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [August 27, 2013, 7:03am UTC](https://boards.straightdope.com/t/what-is-pink-light-can-it-be-monochromatic/667264/10 "2013-08-27T07:03:19Z")
> [@njtt](#): > > Next problem: brown light. 😛 Brown is just dark orange-yellow, so it’s possible that a faint monochromatic lighsource somewhere around 590 nm would look brown. ---
**Author:** ![thelurkinghorror](https://avatars.discourse-cdn.com/v4/letter/t/7c8e57/32.png) [@thelurkinghorror](https://boards.straightdope.com/u/thelurkinghorror)\ **Post date:** [August 27, 2013, 7:40am UTC](https://boards.straightdope.com/t/what-is-pink-light-can-it-be-monochromatic/667264/11 "2013-08-27T07:40:22Z")
> [@njtt](#): > > Next problem: brown light. 😛 They’re making white/pink noise analogies up above. The last person to study the [brown noise](http://en.wikipedia.org/wiki/Brown_note) did not wish to repeat the experience. ---
**Author:** ![njtt](https://avatars.discourse-cdn.com/v4/letter/n/ecd19e/32.png) [@njtt](https://boards.straightdope.com/u/njtt)\ **Post date:** [August 27, 2013, 10:07am UTC](https://boards.straightdope.com/t/what-is-pink-light-can-it-be-monochromatic/667264/12 "2013-08-27T10:07:20Z")
> [@Mangetout](#): > > Brown is just dark orange-yellow, so it’s possible that a faint monochromatic lighsource somewhere around 590 nm would look brown. Actually I am pretty sure it would not, at least, not if was the only source of light in a darkened room (and perhaps not under any circumstances). My “question” was not altogether serious. There is no such thing as brown light. Surfaces appear brown only by contrast with other surfaces in the field of view. If brown completely fills the field of view it will indeed appear as dim orange or yellow. The point to bear in mind is that not all experienced colors necessarily correspond to a wavelength of light, or even a mixture of wavelengths. The relation between color experience and the physics of light is far more complex than that. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [August 27, 2013, 2:29pm UTC](https://boards.straightdope.com/t/what-is-pink-light-can-it-be-monochromatic/667264/13 "2013-08-27T14:29:30Z")
Of course there’s brown light. You can see brown on your computer monitor, can’t you? ---
**Author:** ![AaronX](https://avatars.discourse-cdn.com/v4/letter/a/7bcc69/32.png) [@AaronX](https://boards.straightdope.com/u/AaronX)\ **Post date:** [August 27, 2013, 3:01pm UTC](https://boards.straightdope.com/t/what-is-pink-light-can-it-be-monochromatic/667264/14 "2013-08-27T15:01:42Z")
Why does purple appear the same as a combination of blue and red light? Does it stimulate the red receptors as well? ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [August 27, 2013, 3:21pm UTC](https://boards.straightdope.com/t/what-is-pink-light-can-it-be-monochromatic/667264/15 "2013-08-27T15:21:44Z")
Purple _is_ a combination of blue and red. The question you probably meant to ask was why violet looks similar to purple. To which the answer is mostly what you said, with a nuance: All light stimulates all of the receptors, but to various degrees. Differences in hue are due to the relative amounts that the different receptors are stimulated. It so happens that the red receptors have a fairly fat tail, but the green receptors don’t, so violet light stimulates both red and blue to some degree, but only very little green. ---
**Author:** ![njtt](https://avatars.discourse-cdn.com/v4/letter/n/ecd19e/32.png) [@njtt](https://boards.straightdope.com/u/njtt)\ **Post date:** [August 27, 2013, 5:28pm UTC](https://boards.straightdope.com/t/what-is-pink-light-can-it-be-monochromatic/667264/16 "2013-08-27T17:28:26Z")
> [@Chronos](#): > > Of course there’s brown light. You can see brown on your computer monitor, can’t you? I am not sure if you are joking or not. If you are being serious, you are wrong (and did not very carefully read what I said). No, there is no brown light and, as I said, the relationship between the colors we experience and the physics of light, and even the physiology of the retina, is not at all straightforward. As I also said, surfaces appear brown only when there are other contrasting colors in your field of view. This, of course, is the case, when there is brown on your computer monitor. Even if the brown entirely fills your screen, there is much in your field of view beyond the frame of the monitor. On the other hand, if you could arrange for light of the same mixture of wavelengths as are coming from the brown area on your screen to completely fill your field of view, it would appear orange or possibly some reddish or yellowish shade, not brown. > [@](#): > > Originally posted by [**Wikipedia**](http://en.wikipedia.org/wiki/Brown#Optics) (bolding added): > As a color of low intensity, brown is a tertiary color: a mix of the three subtractive primary colors is brown if the cyan content is low. **Brown exists as a color perception only in the presence of a brighter color contrast.** [15] Yellow, orange, red, or rose objects are still perceived as such if the general illumination level is low, despite reflecting the same amount of red or orange light as a brown object would in normal lighting conditions. ---
**Author:** ![thelurkinghorror](https://avatars.discourse-cdn.com/v4/letter/t/7c8e57/32.png) [@thelurkinghorror](https://boards.straightdope.com/u/thelurkinghorror)\ **Post date:** [August 27, 2013, 7:12pm UTC](https://boards.straightdope.com/t/what-is-pink-light-can-it-be-monochromatic/667264/17 "2013-08-27T19:12:02Z")
> [@Chronos](#): > > To which the answer is mostly what you said, with a nuance: All light stimulates all of the receptors, but to various degrees. Differences in hue are due to the relative amounts that the different receptors are stimulated. It so happens that the red receptors have a fairly fat tail, but the green receptors don’t, so violet light stimulates both red and blue to some degree, but only very little green. If anything, the right (long wavelength/redder) tail is fatter, not the left. Are you looking at the [color matching functions](http://cvrl.ioo.ucl.ac.uk/cmfs.htm) or [cone fundamentals](http://cvrl.ioo.ucl.ac.uk/cones.htm)? (check plot and click submit. the first section in each is sufficient for our purposes). The former is not quite the same thing; it means that if shown an e.g. 450nm light, you have to add lots of blue and less red/green to match it. ---
**Author:** ![Trinopus](https://avatars.discourse-cdn.com/v4/letter/t/2bfe46/32.png) [@Trinopus](https://boards.straightdope.com/u/Trinopus)\ **Post date:** [August 27, 2013, 8:16pm UTC](https://boards.straightdope.com/t/what-is-pink-light-can-it-be-monochromatic/667264/18 "2013-08-27T20:16:48Z")
> [@njtt](#): > > . . . the brown area on your screen to completely fill your field of view, it would appear orange or possibly some reddish or yellowish shade, not brown. I’ve seen that demonstrated. They take an ordinary chocolate bar, and put it side by side with an orange color plate. They really are the same color. It kind of boggles the eye. ---
**Author:** ![AaronX](https://avatars.discourse-cdn.com/v4/letter/a/7bcc69/32.png) [@AaronX](https://boards.straightdope.com/u/AaronX)\ **Post date:** [August 28, 2013, 1:02am UTC](https://boards.straightdope.com/t/what-is-pink-light-can-it-be-monochromatic/667264/19 "2013-08-28T01:02:53Z")
> [@Chronos](#): > > Purple _is_ a combination of blue and red. The question you probably meant to ask was why violet looks similar to purple. > > To which the answer is mostly what you said, with a nuance: All light stimulates all of the receptors, but to various degrees. Differences in hue are due to the relative amounts that the different receptors are stimulated. It so happens that the red receptors have a fairly fat tail, but the green receptors don’t, so violet light stimulates both red and blue to some degree, but only very little green. Oh, that’s interesting, so it’s a single wide peak instead of 2 peaks? ---
**Author:** ![antechinus](https://avatars.discourse-cdn.com/v4/letter/a/fbc32d/32.png) [@antechinus](https://boards.straightdope.com/u/antechinus)\ **Post date:** [August 28, 2013, 3:24am UTC](https://boards.straightdope.com/t/what-is-pink-light-can-it-be-monochromatic/667264/20 "2013-08-28T03:24:06Z")
> [@njtt](#): > > I am not sure if you are joking or not. If you are being serious, you are wrong (and did not very carefully read what I said). > > No, there is no brown light and, as I said, the relationship between the colors we experience and the physics of light, and even the physiology of the retina, is not at all straightforward. As I also said, surfaces appear brown only when there are other contrasting colors in your field of view. This, of course, is the case, when there is brown on your computer monitor. Even if the brown entirely fills your screen, there is much in your field of view beyond the frame of the monitor. On the other hand, if you could arrange for light of the same mixture of wavelengths as are coming from the brown area on your screen to completely fill your field of view, it would appear orange or possibly some reddish or yellowish shade, not brown. Brown is blackish orange - it is still brown. Pink is whitish red - it is still pink. [Next page](https://boards.straightdope.com/t/what-is-pink-light-can-it-be-monochromatic/667264.md?page=2)