Talk:Infrared

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General Comment[edit]

The definition of infrared in the opening paragraphs is inconsistent with the text. Authoritative sources (e.g. the McGraw-Hill Dictionary of Scientific and Technical Terms say and the IEEE standard dictionary) define IR as extending down (in frequency) to 1mm or 1000 micrometers.

In terms of overall organization of the article, it would be better to either break some of the subtopics out into their own articles, or at least organize the materials so that it is a bit clearer that the various alternative categorizations of the IR spectrum are not different definitions for IR, but application-specific designations of bands within the broader IR spectrum.

an improvement of the article could be, to add how this can be related to milling and sieving in the chemistry industry and how it might help with these different products of cell culture media. This would give a much wider state of mind on the subject at hand. — Preceding unsigned comment added by 78.147.19.99 (talk) 16:57, 1 December 2014 (UTC)

(An aside, the last comment regarding the orders of magnitude question under "How does this make sense?" below, has it right.) —Preceding unsigned comment added by Neolute (talkcontribs) 15:34, 7 May 2009 (UTC)

Wavelength of Humans wrong?[edit]

The wavelength of 12 µm in the sentence "Humans at normal body temperature radiate chiefly at wavelengths around 12μm (micrometers), as shown by Wien's displacement law." is wrong!
Reasoning:
1. The Wien's displacement law article reads "Mammals at roughly 300 K emit peak radiation at 3 thousand μm K / 300 K = 10 μm".
2. My own calculations give at 37°C = 310,15 K give 9,34 µm.
Or did I forget something????
Michilans (talk) 15:40, 5 July 2010 (UTC)

Miscellaneous[edit]

"IF your computer monitor is warm, the following patch should be coloured infrared"

I like this joke a lot :-D. But technically, all objects above absolute zero radiate infrared, right?

I imagine if something gets cold enough its black body spectrum will have very little infrared in it, with the peak dropping down into the frequencies below infrared. There will still be infrared emission, but I'm not sure if the swatch could be termed to be colored infrared at that point. Maybe it would be colored microwave.

considering that no one can "see" infrared, it seems weird to say that it is colored as such. if the combination of colors creates other colors, then the square can't be "colored" infrared because it would then be a combination. if you say that it just emits or reflects infrared, then the color is still meaningless, because any visible color could do that if it contains IR reflective qualities. and, black would both emit and absorb IR since it absorbs, and it gets hot.


Who wrote that about sunburn? are you sure? "Although relatively harmless, overexposure to IR can cause damage to cells and is the cause of sunburn (despite ultraviolet commonly being thought of as the culprit.)"

Scientific American seems to diagree: http://www.sciam.com/askexpert/medicine/medicine57/ --rmhermen


How does the infrared in remote controls work? How does our sensation of radiated heat work? Does our skin sense infra-red, or does it heat up because of it and we then sense the heat (are the two different?) -- Tarquin 16:47 7 Jun 2003 (UTC)

I put in a few sentences about remote controls. As for skin, it senses heat, not radiation directly. There is a difference. Direct radiation sensing, as happens in the eye, is a photochemical process caused by photons colliding with light-sensitive (and, if you're a cat, IR-sensitive) molecules. These molecules are highly selective about what wavelength of photon they respond to, which is why we can see in colour. Heat receptors in the skin are different. It seems that nobody knows how they work, but they just sense temperature in the bulk of the skin. This temperature is mediated by mechanical vibrations of atoms, not by radiation. The skin receptors don't know if the heat got there by IR radiation, or by conduction from a hot object. By the way, some snakes can see infra-red, too, but they do it in a different way from mammals with IR-sensitive eyes. Their IR sensors, called pits, are separate from their eyes. The pits detect IR by its heating effect on the skin inside the pit. They can work out which part of the pit is hottest, and therefore roughly where the hot object is. -- Heron

thanks! The above is probably enough to make a start on Thermoception. -- Tarquin 19:45 7 Jun 2003 (UTC)

I find it cool how the Military has grasped this technology to make infrared goggles. —Preceding unsigned comment added by 216.227.15.93 (talk) 12:57, 14 May 2010 (UTC)


The page happens to be in 4 (possibly 5) different categories that mean the same thing. This wiki definitely needs to merge categories to lower their numbers.

Infrared as a color - physical significance?[edit]

Do you have any way to modify the human eye so that we can see infrared as a color?? This should be known by 2100.

Our retina's red-sensing cones are far more sensitive to long wavelengths. The green and blue cones aren't going to give much of a signal. See http://www.4colorvision.com/files/photopiceffic.htm . So, if we view some light which is well above 700nM wavelength ...and if that light is so bright that it does become visible, then it will appear to be deep red in color. This is different than with some digital cameras which "see" infrared as orange or even turquoise color. The three RGB (CYM?) filters on the camera CCD may pass differing amounts of NIR, and if the blue filter passes more NIR than the red filter, the camera will see NIR light as being bluish. --Wjbeaty 19:23, 28 May 2006 (UTC)
It should? omigosh I better get to work then! WTF?!--Deglr6328 16:31, 16 Aug 2004 (UTC)
http://www.amasci.com/amateur/irgoggl.html Yes, and for $10.00. --Alexander
Even for less, just take a IR-fluorescence card for €0.10.--BoP 07:44:59, 2005-09-09 (UTC)

One of the historical discoveries was that the IR radiation boundaries had no physical significance, but was arbitrarily placed due to physiology. Where should I place that in the article? History?--Rayc 03:03, 9 September 2005 (UTC)

Can you give me a hint which physical properties have "physical significance" in current setting of wavelength regions? Today IR is subdivided mainly by the detector range, the transmission windows in an optical fibre and the sources available. Think of Terahertz radiation, some years ago this region was just an uninteresting subportion of IR-or mm-waves. What is the "physical significance" you want to mention? --BoP 07:44:59, 2005-09-09 (UTC)

Not everoyne is physically the same, some people are more sensitive to IR than others71.58.198.190 (talk) 04:40, 17 May 2011 (UTC)

Applications[edit]

I think the article is good so far. One of the things I missed in it was Remote sensing. In a Remote Sensing grad class I took several years ago we focused on biomass and plant stress measurements from the Landsat program images, high Near-IR reflectance for healthy plants. A good discussion of this can be found in http://rst.gsfc.nasa.gov/Sect3/Sect3_1.html

Another simplistic sensing use I saw in a documentary was imaging polar ice to find polar bears, ice reflects IR and polar bears absorb IR (not sure of the band likely near-IR from the images shown). Boris58 22:54, 27 September 2006 (UTC)

How about gaming applications, for example the Wii? This is also creating interest in homebrew hacks on the wiimote such as Johnny Chung Lee's Wii projects Zlog (talk) 12:44, 20 January 2008 (UTC)

As well as gaming applications, some mobile phones also use infrared, although Bluetooth is used mainly. Wikiert (talk) 18:07, 23 October 2008 (UTC)

There is a less popular application that the use of infrared heat is utilized. The asphalt industry used infrared machines to heat asphalt in place to repair and decorate areas. This is a industry that is becoming more popular by the day because of its respect to "green". This application of infrared technology has been in use since the 1970's. --Colinkeinath (talk) 21:09, 28 October 2009 (UTC)

Fahrenheit and Celsius scales[edit]

The image only has a Fahrenheit scale. Does anybody know how to add a Celsius scale to it? Bobblewik  (talk) 12:16, 10 Oct 2004 (UTC)

Done. --Heron 09:37, 12 Nov 2004 (UTC)

what danger can infrared cause?[edit]

It's non-ionising, so the only danger is due to heating. In other words, if it's powerful enough, it will burn your skin. --Heron 09:08, 12 Nov 2004 (UTC)

This is only true in a certain range of pulse lengths and intensities. There are several effects involved at higher intensities (like these found in lasers), like multiphoton processes, plasma generation and such. But in the low intensity case the heating effect is the dominant. --BoP 11:44, 2 Jan 2005 (UTC)
Besides the heating also electrical effects might influence particles at the resonant frequencies, this is where the particle has about the size of the radiation. Which is neglible for humans in the range below 2mm radiation. However cm long waves have shown that they can affect the hair of certain animals... --BoP 07:44:59, 2005-09-09 (UTC)
Related to the dangers of IR, in the "Different Regions in the Infrared" section, there is a mention that the 1530-1560 nm range is mainly used for long-range telecommunications. I've heard that this range is considered the "eye-safe" range. See here for a definition of "eye-safe". In general, I think the information in the previous link and this one from the same website explain some useful but simple ideas that could be incorporated into the article (if not already) such as why near-infrared light is able to permanently damage eyes, and 1.4+ micron light doesn't. This sort of gives context to why you shouldn't ever point a "laser" at someone's eyes. Or maybe just add a reference somewhere to the wiki article for laser safety, although ideally I think it should be the other way around. Kzero22 (talk) 19:19, 7 July 2010 (UTC)

15 micron band saturation and the greenhouse gas effect[edit]

I am doing some research on the question of the carbon dioxide greenhouse effect. Specifically, some critics of Global Warming claim that the 15 micron band is "optically saturated" for CO2 in the atmosphere. Further increases in CO2 will not have the expected effect, they argue, since the band cannot absorb anymore. There just ain't more 15 micron IR left to absorb. We would appreciate any info you could provide on this question. Specifically, how does the IPCC model IR saturation in the 15 micron band for the climate change predictions?

The center of the 15 micron band is saturated, but increasing CO2 concentration extends the unsaturated wings of the band, thus absorbing more IR radiation with increasing CO2 concentration. [1] treats this in some detail. The author there states that you can *still* increase the greenhouse effect by adding CO2 to the atmosphere if the CO2 level is 10 000 times higher than our CO2 level (3 atmospheres). Wikisteff (talk) 22:38, 12 November 2009 (UTC)

IR is not "Heat radiation"[edit]

The article and discussion here seems to reflect a common misconception about IR that I'd like to clear up. Basically, IR does not equal heat, "heat radiation", etc. Warm/hot objects radiate many wavelengths of electromagnetic radiation ("light"), INCLUDING infrared. Have you ever seen something extremely hot glow red? Or get hotter and glow orange, then yellow, then white? Same phenomenon.It glows IR first, you just can't see it. As for transmission of heat via IR, well yeah. Absorption of any wavelength of "light" warms things, INCLUDING infrared. Um, that's all. Thanks.

  • EDIT*

After adding this comment, I went to clarify the article, and realized that this misconception /wasn't/ reflected in it after all. But in that case, what prompted me to post this and "fix" it? Twilight zone...

The article could be less wishy-washy if it clearly states that infrared "heat radiation" idea is simply wrong. After all, a snowbank puts out mostly microwave for its blackbody spectrum. And a 1000mW laser pointer can burn holes in objects. The IR/heat connection is a widespread misconception that's mostly supported by children's science books. But since we were all children at the start, even some physicists end up believing that IR is "heat radiation." One person who has written about this misconception is the physicist Dr. Chris Bohren, but I don't think his article is online anywhere. See his book on popular science, "Clouds in a glass of beer." --Wjbeaty 19:15, 28 May 2006 (UTC)

There still seems to be something missing in the article on the "heat" topic, it states that "IR light from the sun only accounts for 50% of the heating of the Earth, the rest is caused by visible light." Doesn't some of the heat on the earth come from other forms of electromagnetic radiation from the sun other than visible light? Or is the absorbtion rate for other non-visible electromagnetic waves that the sun produce just too low to count? This should be clarified, since the article also stated that "Light or electromagnetic waves of any frequency will heat surfaces which absorb it." --Tetrakatus 27 June 2006

Other heat-adding or heat-cooling mechanisms include:
* radioactive decay (adds heat);
* electromagnetic energy (adds heat);
* volcanic activity (chills surface, heats atmosphere)[1];
* solar wind (adds insignificantly)[2];
* lunar tidal heating (may influence additional volcanic activity)[3]; and
* greenhouse gases (traps heat).
[1] A. Robock, Volcanic Eruptions and Climate (2000)
[2] B. E. Wood, Astrospheres and Solar-like Stellar Winds (2004)
[3] J. G. Williams et. al, Lunar Power Dissipated by Tides and Core-Mantle Interaction (2000)
Hope that helps.
--User:Thangalin 23 September 2006

Excuse me, I think this sentence in the Apps->Night-vision paragraph is a bit screwed up, could some native speaker take a look at it...? (you can delete this post afterwards) [bkil] 17:12, 11 July 2005 (UTC)

Smoke is more transparent to infrared than to visible light, so fire fighters use infrared imaging equipment when working in smoke-filled areas because it does not interfere with other devices in adjoining rooms - this is especially important in areas of high population density (IR does not penetrate walls).

I believe that a partial sentence describing indoor infrared comms got nixed with one on infrared firefighting equipment. Fixed it. Jaraalbe 20:27, 11 July 2005 (UTC)
Yup, just as I suspected! ;) Tx for your edit! :) 62.201.113.195 21:34, 11 July 2005 (UTC)

Didn't a Canadian, P. M. S. Blackett (poor guy, with those initials!) do research on infrared in WW2? --squadfifteen

The whole article is screwy. IR is not 'light', by definition. I can't take seriously anyone who claims to be talking about physics and then refers to 'infrared light'. — Preceding unsigned comment added by 92.14.30.2 (talk) 23:04, 5 March 2012 (UTC)

Lower boundary of IR[edit]

I've tweaked the article a bit, since there seems to be no strong definition I can find of the exact boundary between visible and IR (I've seen 700nm, 750 nm, 760 nm, 780nm, and 800nm listed in various references and standards.) I've also added a paragraph addressing the issue. --Bob Mellish 18:10, 15 December 2005 (UTC)

Authors who give various IR boundaries just show that they don't understand how retinas behave. Since human retinas have no sharp frequency cutoff, therefore there can be no sharp boundary between IR and visible red light. Here's a good article on retinal response: http://www.4colorvision.com/files/photopiceffic.htm
On the other hand, for almost all practical purposes, 700nM is the boundary between IR and visible light. Our retinas are about 10,000 times less sensitive at 700nM than at the peak at 550nM (the green frequencies.) For scenes illuminated with broadband white light sources, the wavelengths above 700nM have far less than 1% contribution to visible red colors, and are essentially invisible. However, if the intensity of a 700nM narrowband source is cranked up by 10,000 times, it becomes just as visible as green light. Similar things are true of ALL near-infrared wavelengths: to easily see 750nM, turn up the brightness by about 200,000X. To easily see 800nM, turn up the brightness by about 10^7. The lower boundary of IR wavelenghts depends on the brightness and frequency distribution of the light source used as illumination. --Wjbeaty 19:15, 28 May 2006 (UTC)
One important note is that the visual system is stimulated by sources as a power law (see Stevens' power law for reference) with a coefficient between 0.33 and 0.5, depending on the source. That means that being 10 000 times less sensitive in photometric terms corresponds to between 20 and 100 times less sensitive in perceptual terms, which is not an insignificant difference. If one were looking at a monochromatic source in a dark room at 710 nm, one's eyes would certainly adapt to be able to see it as a dim red. You can easily test this by turning on an element on your stove to medium at night, if you have a dark kitchen. Not that I disagree with Wjbeaty, who seems to have it right. However, the lower cutoff adopted for IR matters a lot for the power contained in the infrared. Using 750 nm, the irradiance at the Earth's surface is 32 W/m2 in UV, 503 W/m2 in the visible, and 468 W/m2 in IR. Using 700 nm as a cutoff, the irradiance at the surface is 32 W/m2 in UV, 445 W/m2 in the visible, and 527 W/m2 in the IR. Wikisteff (talk) 22:45, 12 November 2009 (UTC)

Could it be that increasing the intensity is not making the the longer wavelengths more visible but the "red" that is perceived is the result of the natural harmonics present that are at unperceptible levels for lower intensities?Carywt64 (talk) 12:29, 13 October 2009 (UTC)

To Carywt64, received light has essentially no higher harmonics at normally-encountered intensities, as the energy densities required for nonlinear optical effects in most materials can only be found in very high-powered lasers. So it's a real effect of wavelength. Wikisteff (talk) 22:45, 12 November 2009 (UTC)
So what is our consensus for the boundary wavelength? I will request 700nm. But I see that some one changed it today to 740nm. Graeme Bartlett (talk) 12:04, 7 July 2011 (UTC)

Ahooo[edit]

Riiight, it's a wolf. This dangerous animal can be seen at http://coolcosmos.ipac.caltech.edu/image_galleries/ir_zoo/dog.html --Femto 14:20, 6 April 2006 (UTC)

Cellphones[edit]

Can someone add the use of infrared on cellphones. --MarioV 01:05, 1 August 2006 (UTC)

Ice cubes emitting microwave?[edit]

and ice cubes emit mostly microwaves...

It doesn't match. If microwaves start at 1 mm, according to Wien's displacement law the top wavelength should be about 2.9 K! Sure water is frozen at that temperature, but it is not what I mean with just ice cube. --Pinzo 19:49, 4 October 2006 (UTC)

CADPAT[edit]

The Canadian Army uses a type of camouflage called CADPAT that reportedly reduces or conceals IR. Think this should be included?

--JodoYodo

Different regions in the infrared[edit]

This section is lacking in any references and so it is unclear who is using the listed "schemes" or how they are applicable. I have no idea how this information was derived. It could be complete rubbish for all I know. Should the first two "schemes" be scrapped? Thanks. — RJH (talk) 18:55, 3 April 2007 (UTC)

Citations[edit]

Why are there so many sections in this article that are missing citation? --the_hoodie 17:21, 23 May 2007 (UTC)

The fact "Humans at normal body temperature radiate chiefly at wavelengths around 10μm" cites a page that does not contain that information
That was boned by this anon IP edit in Dec. 2008. I'll take it out. Dicklyon (talk) 15:17, 26 October 2009 (UTC)

The link at reference [18] is to a business information site which requires an account. This doesn't seem like a legitimate reference, and could be construed as a company marketing there business research service. — Preceding unsigned comment added by 70.194.1.65 (talk) 16:24, 31 August 2012 (UTC)

Missiles[edit]

homing on to the IR signature of the target aircraft, typically the jet engine exhaust plume.

My understanding was this is NOT true; IR missiles home in on the hot metal of the tailpipe, not on the gases themselves which are too diffuse to track. But then this is old information and I know IR seeker heads have changed since then. The sources I can Google talk about both hot metal and exhaust plumes, but they're not all that great ( a lot are corporations with a product to sell ) so I would hope somebody has a good book they can check.

Eleland 20:07, 25 June 2007 (UTC)

therapeutic uses[edit]

This documents a new one, but there are other, better known therapeutic uses such as for cramps etc. --Espoo 18:08, 27 June 2007 (UTC)


"FIR is also gaining popularity as a safe method of natural health care & physiotherapy. Far infrared thermometric therapy garments use thermal technology to provide compressive support and healing warmth to assist symptom control for arthritis, injury & pain."

The above reads like it came straight from an info-mmercial. Before you know it someone will add some BS about the "benefits" of embedded amethyst crystals in your clothes, or something equally asinine. The marketing jargon should be dropped and simply something to the effect of "insulating garments and wraps can increase blood flow to the extremities, perhaps relieving pain and accelerating healing." Ideally, a legit source should be provided to justify the claim. Also, "compressive support" is completely unrelated to an insulating clothing item, which may or may not be compressive. 143.215.217.47 (talk) 18:37, 13 April 2010 (UTC)

There are few businesses which are selling products on FIR. Here is one such company. Their claims are moderate. Yndesai (talk) —Preceding undated comment added 10:16, 6 May 2012 (UTC).

IR Blaster / IR Blast Diode[edit]

Should something be added about an IR Blaster or IR Blast Diode used to actually create the IR signal?166.20.114.10 15:49, 6 July 2007 (UTC)

Night Vision[edit]

Added a couple of references resolving some year old tags. Rewrote the Night Vision section as it was confusing night vision which deals with infrared light and thermal imaging which deals with infrared radiation. Arcos9000 04:36, 13 August 2007 (UTC)

Thermography copyright violation[edit]

In November 2006, user 70.91.43.253 replaced the entire Thermography section of the article with text copied from http://www.infraspection.com/FAQ.html. (Here's a link from archive.org, showing that they had the text before it was added to Wikipedia.) I've reverted the section to the previous version.  --mconst 01:16, 2 November 2007 (UTC)

Wavenumbers[edit]

Can we add wavenumbers (cm-1) into this article. They are an extremely common way of measuring infrared frequencies

what is the history of infrared rays? KALIY Smith —Preceding unsigned comment added by 75.49.37.47 (talk) 00:48, 20 March 2008 (UTC)

Heat - Infrared - The resulting frequencies from external stimuli[edit]

I have been wondering for years: There are apperantly infinate frequencies for an object to be stimulated with/by. However, I wonder if the heat generated, due to the stimulation, is part of the reaction of the object limited to the infrared range? David Colley 75.0.13.223 (talk) 16:54, 22 March 2008 (UTC)

No.

How does this make sense?[edit]

Towards the beginning of the article it says: "Infrared radiation has wavelengths between about 750 nm and 1 mm, spanning five orders of magnitude." How is 750-1000 five orders of magnitude? Isn't this only 1/4 of an order? Or is there some base other than 10 which is being referenced? Anyone? 65.183.135.231 (talk) 19:03, 19 May 2008 (UTC)

750 nm is 0.75 μm and 1 mm is 1000 μm. Seems like 3 orders of magnitude to me. Thunderbird2 (talk) 19:06, 19 May 2008 (UTC)

Doh!65.183.135.231 (talk) 19:20, 19 May 2008 (UTC)

History cruft[edit]

The history cruft was added by a drive-by anon here; since we don't have anyone we can ask about sources, I recommend we just flush the unsourced stuff. OK? Dicklyon (talk) 19:02, 18 December 2008 (UTC)

Candela for sunlight[edit]

It is strange to mention the candela value of bright sunlight in relation to how much of the sun's energy that reaches earth's surface is IR. Candela is a unit weighted for the perception of humans, so all IR light will have an irradiance of 0 candela, no matter how bright. "Bright sunlight provides luminance of approximately 100,000 candela per square meter at the Earth's surface." I would instead use the total radiant flux of the sun across all wavelengths.

122.161.6.100 (talk) 11:05, 23 August 2009 (UTC)

Hey, I just fixed the candela and lumens per Watt to be something more useful, along the lines of your initial comment. Wikisteff (talk) 22:50, 12 November 2009 (UTC)

Article[edit]

Is the subject of this article supposed to be infrared, or infrared radiation? "Infrared" can imply something broader, such as interactions with matter, and "IR radiation" is more specific. Which is it? Tranh Nguyen (talk) 04:54, 15 October 2009 (UTC)

It appears to be infrared radiation, broadly construed, including applications. Dicklyon (talk) 04:56, 15 October 2009 (UTC)
So shouldn't the article be titled "Infrared Radiation"? The ambiguous "Infrared" as a title seems odd, and implies a wider discussion of heat, etc. Tranh Nguyen (talk) 05:02, 15 October 2009 (UTC)
I think the current title is fine. If there's some other infrared topic that needs to be distinguished, show us and we can consider what to do. Dicklyon (talk) 05:03, 15 October 2009 (UTC)
Be sure to cite your sources when you add information, so we can verify it or express it better to agree with the source. Dicklyon (talk) 06:49, 15 October 2009 (UTC)

Frequency values.[edit]

Infrared radiation is right at the intersection of two different schools of measurement: The first being the measurement of visible light (commonly measured by length), the second being the measurement of radio frequencies (commonly measured by frequency).

As a result, it's important to list the ranges of infrared using both wavelength and frequency. I've added frequency values in the lead section of the article. InternetMeme (talk) 11:36, 26 November 2009 (UTC)

Solar Irradiance[edit]

In Raymond S Bradley's book Paleoclimatology the figure of 342 wm-2 but it is not broken down. The figure given in the article is 1kwm-2 and is broken down. Can someone explain the difference between these two figures? Wilmot1 (talk) —Preceding undated comment added 10:16, 10 December 2009 (UTC).

Heat Seeking Telescope[edit]

The Times:-Dominic Dyer, chairman of CWI. “These animals are being wiped out by poachers who are increasingly well equipped with automatic weapons, GPS satellites, night-vision kit and heat-seeking telescopes to spot animals at night."

Do these heat seeking telescopes home in on the animals and automatically control the positioning of the telescopes to track them? Isn't this how the Spitzer Space Telescope works? Kwenchin (talk) 01:53, 21 March 2010 (UTC)

I think the source quoted in this Wikipedia entry only refers to latitudes similar to the US average latitude. — Preceding unsigned comment added by 81.178.192.32 (talk) 18:23, 22 October 2012 (UTC)

"Infrared filters" copyright violation[edit]

The section "Infrared filters", added in October 2007 by user USNV, seems to be mostly copied from the U.S. Night Vision website. (That site has changed in the meantime; the link is from archive.org, showing that the site had the text before it was added to Wikipedia.)

It's not an exact copy -- several words have been changed, and there's one original sentence, but the majority of the text is identical. Even the idiosyncratic capitalization ("all Generations of night vision") has been preserved.

To be safe, I've removed the whole section, but please feel free to add back the original sentence if you think the article would be better that way.  --mconst (talk) 10:08, 26 July 2010 (UTC)

Is or was infrared ever called infared?[edit]

This is what I had thought until a while ago. I notice that "infared" redirects here. Also, the spelling without the "r" appears in the history section in 1945. —Preceding unsigned comment added by 78.151.214.93 (talk) 21:12, 29 November 2010 (UTC)

Just typos. Fixed. Dicklyon (talk) 21:51, 30 January 2011 (UTC)

Heat therapy[edit]

Infrared is a tool to apply heat therapy, that in some aspects is better that application by means of a hot vehicle, such as water, or water soaked supports. It seems that IR radiation penetrates more deep into the body. It seems that IR radiation produce vasodilation also. I have been submitted to it to treat pain in cervical and lumbar regions, in a rehabilitation medical facility, with very good results. In Spain, IR lamps are sold in pharmacies, I suppose it is also done universaly. So it surprises me not to find any reference to this application of IR radiation. Apart from my personal experience I do not have referenced sources to support these claims. Can any wikipedist help?--Auró (talk) 14:49, 30 January 2011 (UTC)

You can find books on heat therapy that mention infrared here. You could add a small section this article, with link to heat therapy, and add more there. Dicklyon (talk) 21:50, 30 January 2011 (UTC)

Tank you for your assistance. I have added a section in "Heat therapy" article, and added a link to it in this article. I plan also to make a new section in "Infrared heaters" article.Auró (talk) 18:32, 13 February 2011 (UTC)

Two passages with citations removed without explanation[edit]

See this diff: http://en.wikipedia.org/w/index.php?title=Infrared&diff=519847450&oldid=519847148 .

I have not delved into the sources to see if they are bunk or not, but removal of cited content without explanation is frowned upon. Would be good to have some words from the editor. --User:Ceyockey (talk to me) 23:27, 25 October 2012 (UTC)

Agree. I thought it was a poor removal myself. Discovery of an near IR sensing fish is neat, and certainly deserves ONE mention. If referenced, it's up to the remover to justify removing it again. I've cleaned out the names (we usually don't include names in these articles, except of REALLY famous scientists), and cut the mention of this primary paper to just once. Hopefully, that will fix the problem. SBHarris 00:34, 26 October 2012 (UTC)
Thanks, Sb ... glad I asked and received a 'second' on the poor removal. --User:Ceyockey (talk to me) 00:44, 26 October 2012 (UTC)

infrared reflectography[edit]

Hello, there is a redirection link from infrared reflectography to infrared. There are dedicated articles in several other languages (fr/it/es), it may be better (?) to have a red-link to be filled with a dedicated article in English latter ? (Sorry for my English, I am French) v_atekor (talk) 11:47, 21 April 2013 (UTC)

Visibility[edit]

It would be nice to have a section (or subsection) on the visibility of near-infrared. A class 1 1064 nm Neodymium:YAG laser shined into dark-adapted eyes is clearly visible, although the upper limit of class 1 is way too much power for maximum color saturation. For peak saturation, you need an average value of 0.069 mW.

(By the way, I support 700 nm as the dividing line. "Visible light" is just a convenient (easy-to-remember) approximation of what most people can see reasonably well under most circumstances.)

Sources:

Relative Luminosity in the Extreme Red

On the sensitivity of the eye to the infra-red limit

The Sensitivity of the Human Eye to Infra-Red Radiation

Foveal Sensitivity of the Human Eye in the Near Infrared

Visual sensitivity of the eye to infrared laser radiation

Absolute sensitivity of the eye in infra-red spectrum

Near infrared light absorption in the human eye media

Infrared color reversal[edit]

The colour of light of very long wavelength

Above 704 nm colors reverse and trend back towards orange. Color Vision: From Genes to Perception [1]

Photoreceptor spectral sensitivities: common shape in the long-wavelength region Lamb, TD (1995). "Photoreceptor spectral sensitivities: common shape in the long-wavelength region". Vision Research 35 (22): 3083–3091. doi:10.1016/0042-6989(95)00114-F.  Absolute sensitivity of the eye in infra-red spectrum

Zyxwv99 (talk) 01:38, 14 October 2013 (UTC)

Fixes needed in "Sensor response division scheme"[edit]

"The onset of infrared is defined (according to different standards) at various values typically between 700 nm and 800 nm, but the boundary between visible and infrared light is not precisely defined. The human eye is markedly less sensitive to light above 700 nm wavelength, so longer wavelengths make insignificant contributions to scenes illuminated by common light sources. However, particularly intense near-IR light (e.g., from IR lasers, IR LED sources, or from bright daylight with the visible light removed by colored gels) can be detected up to approximately 780 nm, and will be perceived as red light. Sources providing wavelengths as long as 1050 nm can be seen as a dull red glow in intense sources, causing some difficulty in near-IR illumination of scenes in the dark (usually this practical problem is solved by indirect illumination). ..."

This paragraph has the following issues:

"between 700 nm and 800 nm" should be "between 680 nm and 800 nm"

"...but the boundary between visible and infrared light is not precisely defined." This is confusing two separate issues and OR. The thing that is getting confused is the literal meaning of "visible" with conventional definitions of "visible light." The boundary is very precisely defined by several different authorities, e.g., CIE, ISO, etc. These boundaries are conventional and don't agree with each other because in the real world the sensitivity of the human eye gradually tapers off.

"The human eye is markedly less sensitive to light above 700 nm wavelength, so longer wavelengths make insignificant contributions to scenes illuminated by common light sources." Nothing happens at 700 nm wavelength other than "visible light" ends by the most widely cited definition of "visible light." This statement could equally apply to 680 nm, 800 nm, or any wavelengths in between.

"...can be detected up to approximately 780 nm..." Nothing happens at 780 nm other than the CIE scotopic luminosity function ends at 780 nm, as does the abridged version of the CIE photopic luminosity function (unabridged ends at 830 nm). Once again, someone seems to be taking conventionalized definitions are reading too much into them. By this logic, the weather should suddenly get better on the first day of spring.

"Sources providing wavelengths as long as 1050 nm can be seen as a dull red glow in intense sources..." The only range of wavelengths I've ever heard of that always looks like a dull glow is about 290 nm - 305 nm. At 310 nm children and young adults still have some visual acuity. Below 290 nm people tend to see nothing. At 300 nm those who see anything at all tend to see only their own eye fluorescence, mainly lens fluorescence. No such problem occurs in the infrared, except with sources that are prone to producing dull glows. Furthermore, "red" is not necessarily correct either. Although 1050 nm usually looks red, it can also look white or any of several other colors depending on whether it is flickering or seen in peripheral vision.

Any finally, only the 1050 nm number is supported by the reference (for scotopic vision, 1000 nm for photopic). Everything else looks like OR. Zyxwv99 (talk) 14:12, 24 October 2013 (UTC)

Visible or invisible?[edit]

The first paragraph needs to sound less self-contradicting:

"Infrared (IR) is invisible radiant energy [...] although people can see infrared up to at least 1050 nm in experiments[2][3][4][5]".

Unless, of course, the experiments took place in the Twilight Zone. 5.12.167.196 (talk) 18:05, 2 August 2014 (UTC)

Actually it's not just in vision experiments. Nowadays huge numbers of people work with near-infrared lasers and can see the light. With broadband sources such as diodes you can't be sure what you're seeing because the dominant wavelength (perceived wavelength) can be a great distance from the peak wavelength. (To calculate dominant wavelength get the spectral curve with a digital spectrometer, slice it into 1 or 5nm slices, then adjust each slice for the sensitivity of the human eye at that wavelength, then find the midpoint of the area under the curve.) The two most common wavelengths of infrared laser pointers are 808nm and 980nm. The dot from a weak (5mW) 808nm is clearly visible at night in a dark room, even though the sensitivity of eye at that wavelength is only 1/2 millionth as great as at 555nm (wavelength of peak sensitivity). At 980nm it's only about 1/2 billionth, but you can still see the light when shined directly into the eye. (Not recommended, especially as many of the cheap ones sold on eBay for $15 are 2-20 times as powerful as advertized.) Millions of people own these lasers. The 980s are used in China for fake currency detection. Their visibility is common knowledge. Also, technicians who work with fiber optics routinely report seeing infrared in the low-mid 800s. The problem is that the visible portion of the near-infrared spectrum is less than 0.05% of the entire infrared spectrum, and is only visible from narrow-band sources such as lasers. That's makes the wording a bit tricky. Zyxwv99 (talk) 02:13, 3 August 2014 (UTC)
    • ^ Lamb, Trevor (28 May 2001). Karl R. Gegenfurtner, Lindsay T. Sharpe, ed. Color Vision: From Genes to Perception. Cambridge, UK: Cambridge University Press. pp. 93–4. ISBN 978-0-521-00439-8. Retrieved 12 October 2013. (p 93)...a wavelength of 800 nm (which elicits an R/G ratio of about 12) should appear the same color as a wavelength of 663 nm...(p 94)...reversal occurs at a wavelength of about 704 nm