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Archive 1

Semiprotected

I have semiprotected this page from editing from anon and new users due to reports of persistant vandalism from IPs registered to public schools in the State of Nebraska. Please request unprotection at Wikipedia:Requests for page protection when appropriate. -Loren 17:20, 15 February 2006 (UTC)

Some people define radio freqeuncy as the range from 3kHz to 1GHz, i.e., they don't include the microwave range. But here the microwave range is inluded in the radio frequency, I thought this needs some clarification....

frequency v?

What are we using v to represent frequency? Am I wrong to consider f a more apt choice of variable?

Zeta

Using the Greek letter nu (ν) to represent frequency is quite common in physics. Using f might be more appropriate for an introductory article like this one, I don't know. Pfalstad 01:58, 16 May 2006 (UTC)

Unit consistency

The units for labelling the spectrum chart at top right include some curious choices: da (presumable deca), d (deci) and h (hecta) are rarely used either in scientific fields nor common language. From experience as an engineer, these would be greeted with ridicule by anyone with a scientific background, incidentally neither of them are recommended as ISO multiples (nor is cm). For consistency, these would be better shown using the standard multiples (nm, um, mm, m, km, etc.) of m only, with a multiplier of 10 or 100 where necessary.

I agree somewhat. But it is also somewhat culturally determined. In Netherlands (where I live) wheather reports mention pressures in mbar, while in Dutch-speaking Belgium, as well as in Sweden, they use hPa. The unit dm is sometimes used in common language over here. In my field of science (spectroscopy), the cm is used very often for things like intensity (W/cm2) and inverse wavelength (cm-1). Han-Kwang 10:27, 8 June 2006 (UTC)
Granted, there may be cultural/common-use differences, but I wouldn't like to rely on them as a pointer for use in a technical/scientific document (we still use inches, feet and miles in england for measuring people/clothes/road distances, but no draughtsman would even dream of dimensioning a drawing with them). Also, I am very surprised that a professional branch of science is using a non-ISO measurement unit - in my experience, not a single industry (electronic, construction, mechanical, architectural) has used them. --Inzy 00:23, 25 June 2006 (UTC)

Image formatting

what the hell is wrong with the image formatting on this page?--68.121.86.23 01:40, 17 October 2006 (UTC) ALSO: frequencies should be arranged lowest to highest...

Misleading Comparaison

The comparision between what i assume is the Alternating current system used for power grids (50htz here) and the low end of the EM spectrum. I made a minor edit that emphasises that electricity is not part of the em sepctrum but i think it still needs revision.---bladeScythe 10:45 19 August 2006 (EST)

I checked for any actual connection between electricity and ELF but couldnt find any. A comparison of frequencies between electricity and light is an irrelevant one, so I replaced the refrence to electricity with "radio" since radio waves are the lowest commonly used frequency.Mloren 12:52, 19 August 2006 (UTC)

== UNABLE TO READ

Sorry, but I can't read this page because this article is unable to read !! 83.23.248.244 19:34, 22 January 2007 (UTC)

Sorry of my English, I'm living in Poland and I'm learning English

inconsistency with ELF image

The chart on this page (and the identical one in Electromagnetic radiation) is not consistent with page on ELF which gives the frequency range of ELF as 3-30 Hz, not 30-300 Hz (which is SLF). Also, instead of using VF for the range of 300-3kHz, it would be more consistent to use ULF. DaraParsavand 20:18, 12 March 2007 (UTC)

Limits of the EM spectrum

I saw this quote "It is commonly said that EM waves beyond these limits are uncommon, although this is not actually true." Limits being "from thousands of kilometres down to fractions of the size of an atom." Can someone give a source for this or explain it please? 70.124.85.228 12:19, 14 August 2007 (UTC)

You mean a source for "commonly said that"? I'm not sure what is there that needs explaining. Han-Kwang (T) 13:22, 14 August 2007 (UTC)

layout

there's way too many pictures and not enough text!!!! but good job on this thing! =] Lady Nimue of the Lake 10:55, 4 September 2007 (UTC)

hehe —Preceding unsigned comment added by 194.154.22.53 (talk) 10:35, 7 September 2007 (UTC)

messed up completely

Some one messed up completly on this —Preceding unsigned comment added by 70.188.191.92 (talk) 23:46, 4 October 2007 (UTC)

Don't know if you think it's too much, but if reciproc centimeters was added to the other units I think it would be perfect. Even though it properly need a little text to be explained. It is very used in spectroscopy and would be nice to have next to the other units. Sorry for the bad spelling, that's why I don't do any direct editing :) —Preceding unsigned comment added by Nanopete (talk • contribs) 14:32, 8 October 2007 (UTC)

Planck Length

I have changed part of the introduction to read "...the short wavelength limit is likely to be in the vicinity of the Planck length...". This corrects a common misconception about the Planck length, namely that it is a directly meaningful physical quantity which defines a precise limit where one type of physics ends and a new type begins. In reality, its construction is fairly arbitrary (for example, there is no physical justification for using h-bar instead of h), and thus it only provides an order of magnitude estimate for the length scales of quantum gravity. Hyperdeath (talk) 12:46, 30 December 2007 (UTC)

Layout changes

I made some changes to the formatting and layout of images, as well as to the math, but I didn't realize i wasn't logged in. I appologize.

Tiny.ian (talk) 21:49, 4 January 2008 (UTC)

Range of electromagnetic spectrum

I always thought that the electromagnetic spectrum ranges from 0 to 1 to 10^24 to 1/0 (undefined) Hz.--Mathsexpressions 00:03, 17 March 2007 (UTC)

There is nothing about the lowest measured wavelength/highest frequency of gamma radiation. —Preceding unsigned comment added by 86.138.30.152 (talk) 03:27, 16 March 2008 (UTC)

Electromagnetic radiation

This article covers very similar territory to Electromagnetic radiation. Shouldn't they be merged? -- The Anome

This article is very similiar in topic to that one ... JDR

No, I think there is two different types of information in the articles. Merging would not make sense. --ScienceMind (talk) 11:26, 27 July 2008 (UTC)

Appropriate Forum?

I'm wondering, is this the proper page to discuss questions about EM radiation, or should we limit it to just discussing the contstruction of the article? Where would be a good place for a novice like me to ask questions about physics issue3s in general? —Preceding unsigned comment added by 63.255.108.25 (talk) 01:20, 29 November 2007 (UTC)

I don't think this is the area for general discussion, it should be about the article. You should join us at physicsforums.com for physics debates! --ScienceMind (talk) 11:31, 27 July 2008 (UTC)

Or on-wiki there is the Science Reference Desk. - Eldereft (cont.) 11:47, 27 July 2008 (UTC)

Try to find a more simple definition for kids!!!

That's a good page but i wanted a simple definition such as- the entire range of electromagnetic waves is called the electromagnetic spectrum. :) —Preceding unsigned comment added by 66.81.29.191 (talk) 01:10, 2 October 2008 (UTC)

You should check out the Simple English Wikipedia for easier definitions. The only bad thing is that we're scarce on articles in Simple English; we don't have an Electromagnetic Spectrum article. -- penubag  (talk) 03:30, 2 October 2008 (UTC)

Radio Frequency/MRI

I removed MRI from the list of applications of radio waves. MRI uses a magnetic field oscillating at radio frequency, but does not use radio waves - it uses the near field, which does not propagate. The section is titled 'Radio frequencies' but describes RF waves - in MRI the distinction is important. GyroMagician (talk) 20:45, 25 December 2008 (UTC)

Image correction

The first image: http://upload.wikimedia.org/wikipedia/commons/a/a9/Light_spectrum.png needs to be corrected. A frequency of 300Hz does not correspond to a wavelength of 1km. It should be changed to 1Mm. —Preceding unsigned comment added by Cmusco618 (talk • contribs) 20:56, 29 November 2007 (UTC)

Also wavelengths of 10dam and 100 hm should read 10m and 100m, but I could not change them.

notthe600 Notthe600 (talk) 10:55, 9 December 2007 (UTC)

Also, the wavelengths that supposedly are stopped by the Earth's atmosphere are nonsense, of course UV light gets through our atmosphere - hence sun burn. And Radiowaves do as well, otherwise the Apollo missions would have failed. —Preceding unsigned comment added by 81.79.216.188 (talk) 20:10, 16 January 2009 (UTC)

Used as source

{{source}} there are sources for??

High energy gamma rays Creation of particle-antiparticle pairs. At very high energies a single photon can create a shower of high energy particles and antiparticles upon interaction with matter.

187.4.208.77 (talk) 14:27, 19 March 2009 (UTC)

This is the most common means of detection of very high energy gamma rays, a bit of discussion can be found at, for instance, [1]. 69.140.12.180 (talk) 22:07, 26 May 2009 (UTC)Nightvid

Before I got to this section of the talk I rated this article as a WOW!
(really good job!) Ti-30X (talk) 13:35, 31 May 2009 (UTC)

EM spectrum chart error

The chart at the top of the page, Image:EM_Spectrum3-new.jpg, must be incorrect, because some of the sun's UV rays do penetrate the Earth's atmosphere. If they did not, people would not be able to get tanned or sunburned naturally. --Kyoko 21:00, 16 January 2008 (UTC)

I've inquired a scientist for his opinion (pending...), I'm not an expert at this but the image is made by NASA so it has credibility -- penubag  23:14, 25 January 2008 (UTC)
Image:Ozone altitude UV graph.jpg-- penubag  00:51, 26 January 2008 (UTC)

UPDATE: I have updated the mainpage diagram that should address your concern. -- penubag  23:55, 28 January 2008 (UTC)

The image is still incorrect. These are the correct values

UVA 800 nm - 564 nm UVB 563 nm - 426 nm UVC 435 nm - 203 nm hehehehe

from the "ultraviolet radiation" page. If that picture makes any kind of sense, then UVs should be at least in the grey zones. I think it is too approximate and pictorial, and uninformingly so. Someone should do a better one. --Triptaruga

It's not exact, but does it need to be? I' happy with it the way it is as it's educational to the layperson either way.--ScienceMind (talk) 11:33, 27 July 2008 (UTC)
Plot of Earth's atmospheric transmittance (or opacity) to various wavelengths of electromagnetic radiation.

The chart lower on the page, Image:Atmospheric electromagnetic transmittance or opacity.jpg, seems to claim that the atmosphere is opaque to radio waves longer than about 30 m (10 MHz). If that were true, then medium wave AM broadcasting (520 kHz–1,610 kHz) wouldn't work. Is that a simple error in the chart, or is there something I'm missing here? --68.0.124.33 (talk) 17:05, 19 July 2008 (UTC)

The upper atmosphere is opaque to AM frequencies which allows them to be reflected off the atmosphere and back to earth's surface. This is one reason why AM radio can be received where other radio cannot.163.1.208.166 (talk) 16:15, 10 June 2009 (UTC) UNOTLD ORIGINALITYItalic text

Inclusion of Cosmic Waves in the discussion

I believe that further away from RAdio waves we have cosmic waves. is this true ?? should this also not be added to the article. Ap aravind (talk) 09:12, 16 October 2009 (UTC)

Light Frequencies

The second picture of Electromagnetic Spectrum is also wrong: 10^15 Hz is not visible light (it corresponds to a wavelength of 300nm). —Preceding unsigned comment added by 85.232.195.217 (talk) 08:00, 17 April 2010 (UTC)

Corrected the image file. Materialscientist (talk) 08:40, 17 April 2010 (UTC)

Error in "The electromagnetic spectrum" image

380nm = 7.89*10^14Hz / 750nm = 3.99*10^14Hz / 299.8 = 1*10^15Hz / Frequency 1*10-15Hz is not in visible spectrum ! / Wavelength and frequency measures are errornously shifted. Softvision (talk) 17:27, 23 July 2009 (UTC)

Corrected the image file. Materialscientist (talk) 08:40, 17 April 2010 (UTC)

Edit request from Ennisdb, 15 February 2011

{{edit semi-protected}} In the second figure, the legend incorrectly states "VF/ULF" and it should state "LF/ULF." There is no "VF" spectrum. Ennisdb (talk) 05:08, 15 February 2011 (UTC)

VF is mentioned in the figure, and thus we can't just change the caption. It might mean voice frequency. Materialscientist (talk) 05:25, 15 February 2011 (UTC)

Wavelengths

Somebody put some wavelengths and/or frequencies in?ÇĢÇ+ɭ=92/3

The Wikipedia article on "X-rays" states (with several references) that the distinction between x-rays and gamma rays today is based on origin, not energy; high energy photons generated by nuclear or particle processes are gammas, while those resulting from electron transitions or acceleration are x-rays.173.9.146.174 (talk) 21:51, 24 March 2011 (UTC)

History?

I think this article could use a history section. Does anyone object? Eomund (talk) 04:25, 14 February 2012 (UTC)

Of course not. Everything in WP could use a history section. SBHarris 17:59, 14 February 2012 (UTC)
Well there a start. It could probably use some cleanup and some references. I'll probably take another look at it in a couple of days. Eomund (talk) 04:09, 15 February 2012 (UTC)

Optical Radiation

Infrared, the visible region we perceive as light, and Ultraviolet are now generally brought together under the title Optical Radiation.
It would be good to place this text somewhere in this page. — Preceding unsigned comment added by Arie Klerk (talk • contribs) 18:40, 14 February 2012 (UTC)

This seems to be a sort of regulatory classification, and I don't even know how it would be implemented without some kind of RBE or quality factor to compare the damaging effects to the eyes of 100 nm UV to that of (say) 10,000 nm IR. Perhaps some line about "EM radiation capable of damaging the retina is referred to in occupational safety literature as "optical radiation." SBHarris 21:35, 15 February 2012 (UTC)

Grammer error

In the history section, third sentence, 'studied' should read 'study'. 6th sentence should read temperature 'of' different colors. 14 th should be 'an' apparatus. 2nd last sentence, he first thought 'that they were' particles... — Preceding unsigned comment added by Snzaisuru (talk • contribs)

Fixed as suggested, thanks. Materialscientist (talk) 12:45, 23 February 2012 (UTC)

properties are where ???????? — Preceding unsigned comment added by 121.54.35.178 (talk) 00:57, 28 February 2012 (UTC)

Is this what you are looking for? Eomund (talk) 03:50, 28 February 2012 (UTC)

Error

In visible light section-- "most" of EM radiation output from Sun/stars is NOT visible, though peak intensity can be. See Planck's Law. Not sure why editing is disabled on this page; someone else can fix it if they like.

Welcome to Wikipedia. Pick a username and sign in and you'll be able to edit articles like this one after 4 days and a few good edits. Meanwhile, add ~~~~ = 4 tildes to your posts so they will be autosigned.

Yes, you are right, only about 40% of the EM output of our Sun 1400 watt/meter a the top of the atmosphere) is in the visible band. SBHarris 15:29, 29 April 2012 (UTC)

Red light is made of radio waves?

This image at the top of the page needs work.

  • The colors red and magenta don't extend all the way across the entire spectrum. Magenta's not even a spectral color.
  • "Penetrates Earth's atmosphere" is not a binary thing. The brightness could be varied along with the actual absorbance spectrum. Ultraviolet doesn't pass through the Earth's atmosphere?
  • Things at negative 170 degrees C are red hot?
  • Why isn't the spectrum spaced evenly with the logarithmic powers? The distance between 10^12 and 10^16 is larger than the distance between 10^8 and 10^12
  • File_talk:EM_Spectrum_Properties_edit.svg —Preceding unsigned comment added by 71.167.67.65 (talk) 00:05, 14 August 2010 (UTC)

I second these complaints. This image is very misleading in that it makes radio waves look red. Everything not in the visible portion of the spectrum should be black on the chart because that it what humans see when looking at light sources of non-visible wavelength. Also, the colors are not lined up properly with their frequency values. 74.104.22.121 (talk) 14:51, 29 December 2012 (UTC)

Edit request on 9 May 2012

Add the missing closing parenthesis in 4th (final) paragraph of the "Ultraviolet light" section.

Text presently reads: ... are absorbed by nitrogen and (at longer wavelengths by simple diatomic ...

Text should probably read: ... are absorbed by nitrogen and (at longer wavelengths) by simple diatomic ...

203.206.166.87 (talk) 04:35, 9 May 2012 (UTC)

Tweaked using commas - there were too many brackets in that paragraph already. Thanks. Materialscientist (talk) 05:45, 9 May 2012 (UTC)

== "hello Why is the "The" (first word of the article) not on same line as the sentence? I fiddled with it, no luck. Is this a temporary gliche?--Wyn.junior (talk) 21:29, 11 April 2014 (UTC)

Semi-protected edit request on 6 February 2015

elkectromagnetic is cool

187.188.100.199 (talk) 19:19, 6 February 2015 (UTC)

Not done: it's not clear what changes you want to be made. Please mention the specific changes in a "change X to Y" format. Anupmehra -Let's talk! 21:58, 6 February 2015 (UTC)

Empty column in table

please delete the empty column in table, i cant do it because when i delete it, table crush!--Viliam Furík (talk) 11:10, 30 March 2015 (UTC)

Can we add sound waves perceptible to humans on this chart?

--Wyn.junior (talk) 21:01, 4 May 2014 (UTC)

I hope you don't mind me moving that chart and diagram into the main article. --DavidCary (talk) 16:00, 3 June 2015 (UTC)

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Front table is wrong from 100 micron to 100 nm

The classications of near UV, visible, near IR, mid IR unfortunately do not fall on neat metric-powers-of-ten in wavelength and so the table, for all its elegance, is wrong. Correct classifications that would be consistent with the rest of wikipedia and the rest of the world:

  • 100nm to 380nm: FUV-NUV - Far ultraviolet to near ultraviolet. Note that "near UV" (NUV) itself is only a tiny span, ~ 300-400 nm!
  • 380nm to 780nm: VIS - Visible
  • 780nm to [3-5] micron: NIR - Near infrared
  • [3-5] micron to [25-50] micron: MIR - Mid infrared
  • [25-50] micron to 1 mm: FIR - Far infrared

For the NIR-MIR boundary and MIR-FIR boundary, there is a bit of disagreement (see infrared article) but you might as well peg it on the ISO 20473 scheme, which assigns 3 micron and 50 micron, respectively.

See also Naomi Halas' converter site, which has all the conversions: http://halas.rice.edu/conversions

As for the left column, "ionizing radiation" should go to around the 300 nm level, i.e., not all UV radiation is ionizing. --Nanite (talk) 11:00, 18 November 2015 (UTC)

Semi-protected edit request on 13 June 2016

The word 'color/colour' is spelt inconsistently throughout this article. Please rectify this. As the spelling 'color' currently appears more often than 'colour' I strongly recommend the former spelling is preferred. Thank you.

ManSoAdmired (talk) 16:30, 13 June 2016 (UTC)

Not done: The three occurrences of "colour" are all in quotes in the "Notes and references" section. Quotes have to be given verbatim with the original spelling. Favonian (talk) 16:41, 13 June 2016 (UTC)

That's sound man, but I checked the original source for note 7 and it is spelt 'color' there. So get it changed verbatim quicksharp. — Preceding unsigned comment added by ManSoAdmired (talk • contribs) 17:03, 13 June 2016 (UTC)

Your wish is our command. :P Favonian (talk) 17:07, 13 June 2016 (UTC)

I love you Favonian. Have you heard of Gary Ablett? — Preceding unsigned comment added by ManSoAdmired (talk • contribs) 17:32, 13 June 2016 (UTC)

Beyond the measurable spectrum?

      • !!!***

OMG "Until the middle of the 20th century it was believed by most physicists that this spectrum was infinite and continuous." is WRONG. Ummm... it is STILL BELIEVED TO BE INFINITE.

To assume the EM spectrum is limited to what "most sources" reference is a fundamental miss and this wiki sentence is as preposterous as denying Moore's Law - every frequency we check exists and there is no evidence to say it will end. The mathematics of Maxwell's equation are limited to a finite spectrum? Really? Are infinitely small derivative lengths also finite? THE EM SPECTRUM IS BOTH CONTINUOUS AND INFINITE, BY ASSUMPTION, TO THE BEST OF OUR KNOWLEDGE. This wiki sentence is philosophical semantics. It's like saying, "Until the middle of the 20th century it was believed by most physicists that God and all other deities ('this spectrum') was infinite and continuous. [But today, we know they are finite creations that do not exist beyond empirically measured boundaries]."

1) Any frequency: 1. and 1.000000...001 exist (assume this, because if you care about this stuff beyond philosophical babble than you'll have some empirical knowledge about it - i.e. can measure the effects of the thing). 2) Beyond gamma rays, THERE ARE EM WAVES >> 10^15 Hz and << radio waves (or whatever), you can name them if that makes you feel better, but not sure they have a name unless they are used for something "empirically"

Sidenote: I feel very confident about these simple points, although haven't considered how QED or physics particle theory plays in...

I was wondering, what is beyond gamma rays or ELFs? The first sentence here says

The electromagnetic (EM) spectrum is the range of all possible electromagnetic radiation.

and I'm thinking that, for science's sake, we should reword it to say "all measurable electromagnetic radiation". According to the De Broglie hypothesis, all matter has a wavelength, it's just when you get to sub-atomic particles do the wavelengths have a measurable effect, such as X-rays or color or heat or what-have-you. How does this sound to the wikipedia crowd? Rhetth 02:51, 25 August 2007 (UTC)

Most sources are not very careful in the matter, but the usual definition of radio waves is electromagnetic radiation of wavelength longer than 1 mm, with no longest wavelength, thus there cannot be anything "beyond" radio waves. Similarly, there is no lower limit on the wavelengths of gamma rays.
One can of course point out that only theory holds that the spectrum can extend infinitely, while experimental evidence is confined within finite bounds. To take the lowest and highest frequencies for which direct physical evidence exists to be the "ends" of the spectrum would give a lower limit of < 30 Hz (see for instance http://www.cv.nrao.edu/course/astr534/Pulsars.html ) and, perhaps somewhat
arguably, even < 1 Hz (See the "P-Pdot diagram" on that website, with the longest periods being several seconds, thus if you accept that the loss of rotational energy can be ascribed to radiation of EM waves at that frequency this would qualify). The highest frequency would correspond to the highest energy gamma quantum yet observed from space (nu = E / h, so for E = 12 TeV this is roughly 2.9 * 1027 Hz.)
Taking the limits to be 2.9 * 1027 Hz and 0.133 Hz (corresponding to a period of 7.5 seconds on the P-Pdot diagram), the observed EM spectrum spans over 28 powers of 10, and over 94 powers of 2 or 'octaves'!

-User: Nightvid

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Semi-protected edit request on 13 November 2016

At the bottom of the page, there is a link for "Flash EM Spectrum Presentation / Tool" that has been marked as dead since July 2016. You can actually see that the same content is available here: http://attic.e-motiv.net/em-spectrum

The content is available at the same domain, they just changed the structure a little bit.

Craig Sandez (talk) 05:16, 13 November 2016 (UTC)

Done -- Dane2007 talk 06:32, 4 December 2016 (UTC)

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Semi-protected edit request on 22 December 2016

Please change 

| rowspan="2" style="text-align:right;"| 124  [[peV]]<!---col 7--->

to 

| rowspan="2" style="text-align:right;"| 124  [[picoelectronvolt|peV]]<!---col 7--->

because the tooltip is missing

Thanks

Bageederd (talk) 06:18, 22 December 2016 (UTC)

 Done! DRAGON BOOSTER ★ 06:55, 22 December 2016 (UTC).


Hmm ... it seems there are two competing forms of expression in that table. One which shows just the metric prefix and the other which uses the more appropriate unit to the column it is contained in (e.g. Pico- vs. picoelectronvolt). Would you mind updating that table column so the labeling of the units ends with "electronvolt". It really helps saps like me who have CRS syndrome.

Please & Ty

Bageederd (talk) 08:07, 22 December 2016 (UTC)

 Done! DRAGON BOOSTER ★ 10:35, 22 December 2016 (UTC).

Redundant Image?

At the top of the article, there is a table listing information about the different classes of the EM spectrum. Right below it is what appears to be an image containing exactly the same information. Is there a good reason to have this redundant image? Myoglobin (talk) 20:13, 22 December 2016 (UTC)

Question

If everything in the EM travels at the speed of light, then why does sound travel at the speed of sound?--Wyn.junior (talk) 02:12, 6 May 2014 (UTC)

If all birds have two wings, then why do dragonflies have four wings? --DavidCary (talk) 16:01, 3 June 2015 (UTC)

Sound is not electromagnetic radiation. It is in fact, pressure variation waves in a medium. As will all things, it is quantized, but this reality is not an issue in nearly all circumstances. The exception is largely in the field of material science in which phonon (NOT photon) vibrations travel through materials such as crystals. Examination of those phonons (losses, interference, energy distributions, ...) is sometimes used for analysis. Electromagnetic radiation, on the other hand is the interaction (as described by Maxwell) between electric and magnetic fields and 'packaged' as photons. NO underlying material is required and photons can travel through space. No ether (qv) is required either. 69.118.209.149 (talk) 14:22, 27 December 2016 (UTC)

Semi-protected edit request on 3 January 2017

Please change "1Hz" in "Frequency" column, last row of the first table (table with links) to "3Hz" because 1Hz is the wrong value and the correct value should be 3Hz as stated in the second table (picture) below. Jaredxwos (talk) 12:03, 3 January 2017 (UTC)

Done st170e 12:16, 3 January 2017 (UTC)

Sound

The audible range of the electromagnetic spectrum should be indicated, in the text and table. — Preceding unsigned comment added by 190.102.147.254 (talk) 14:02, 22 February 2017 (UTC)

Electromagnetic radiation iself is not audible at any frequency.DavRosen (talk) 14:49, 23 February 2017 (UTC)

specified name/ labels

how much could be these possible (correct)? :
X-ray: Xeno ray (xeno: strange)
UV: Ultra Vision (still can be seen by some)
infrared: Thermal Radiation, Radiotherm, RT
: after renaming electromagnetic spectrum as radiational spectrum: Radiospectrum
microwave: Magnetocyme (from magnetron, cyme: wave, greek)
: so radio telescope as Cymoscope etc.
radiowave: Electrocyme (from electric currents)
low frequency: Kryptocyme (K from kilometric wave, krypto: hidden)
and finally Macrocyme for the rest (and cosmocyme for deep space radiation; wavelenght of larger than one gigameter)
Tabascofernandez (talk) 08:50, 18 October 2017 (UTC)

Needs image

What we really need here is a good (and colorful!) picture of the visible spectrum!!! Malbi 13:34, 2 December 2003 (UTC)

See Color. Patrick 01:58, 28 January 2004 (UTC)

Removed statements

Removed statement about low wavelength EM being impossible to measure directly. There is no lower limit on wavelength detection, and one should be able to detect arbitrarily low wavelength EM via compton scattering.

Roadrunner 21:34, 1 April 2004 (UTC)

Removed statements (2)

Removed this from the UV section: "It was discovered to be useful for astronomy by a Mariner probe at Mercury, which detected UV that "had no right to be there". The dying probe was turned over to the UV team full time. The UV source turned out to be a star, but UV astronomy was born.". Even if it's true, it's badly written and no proof nor real data is given about it — Preceding unsigned comment added by KJK::Hyperion (talk • contribs) 01:38, 12 January 2005 (UTC)

Periodicity

"It is commonly said that EM waves beyond these limits are uncommon, although this is not actually true. The 22-year sunspot cycle, for instance, produces radiation with a period of 22 years, or a frequency of 1.4*10-9 Hz."

Is this true? If so can we have some sort of source? It seems to me that it might be confusing the periodicity of sun-spots with the frequencies of radiation that might be emitted as a consequence. — Preceding unsigned comment added by 203.202.144.223 (talk • contribs) 04:58, 2 August 2006 (UTC)

Radio Frequencies

Under 'Types of Radiation' the article seems to be going through radiation types in order of wavelength. However for the Radio Frequencies section it includes the entire spectrum from "hundreds of meters to about one millimeter" wavelengths, spectrum which includes the SHF and EHF of the 'microwaves' section below it. It seems that the paragraph intends to describe the narrower range of frequencies used for broadcast rather than the broader range that goes by the technical name 'Radio Frequencies' (which, it should be noted extends to "Extremely low frequency"s with 100,000 km wavelengths rather than the "hundreds of meters" above). If I'm right, the section should probably be rewritten to include only the broadcast frequencies and perhaps an extra section should be added for lowest frequencies. Is my analysis correct here or am I missing something? Rxtreme (talk) 05:17, 19 August 2008 (UTC)

Speed of light

Value of the speed of light corrected in km/s: from 300 (previous) to 300,000. Doctorcito 12:18, 2 August 2005 (UTC)

EM Spectrum "Timeline"

Has anyone made a "timeline" similar to this Vocal and instrumental pitch ranges chart? If not I think one should be started. Anyone want to help? Zhatt 19:51, 9 August 2005 (UTC)

Something that can end up looking like this. Zhatt 22:42, 9 August 2005 (UTC)

SI

What could a chemist do with electronvolts?... Energy levels should rather be mentioned in J, J/mol, or at least both J and eV.— Preceding unsigned comment added by 5.204.15.9 (talk • contribs) 20:03, 28 June 2014 (UTC)

7 or 8 bands?

Some parts of the article references 8 bands of EMR, including the "Terahertz" band; other parts of the article reference 7 bands, moving from microwaves to infrared. What's the deal with Terahertz? Are these talking about two different things and I am misreading it? Thanks Proctris (talk) 16:09, 16 May 2019 (UTC)

Updated EMF table to include all frequencies down to 3 Hz as Radio + someone please remove "microwaves?"

The ITU table for radio waves goes all the way down to ELF, and the ELF article itself states that this band is considered radio waves. As such, I've edited the table to include all bands down to ELF as radio waves.

Additionally, I do not believe we need to label this region "microwaves and radio waves" since microwaves are radio waves per se. An update to the table would be appropriate, but I leave it to someone with better knowledge of Wikipedia's formatting language to perform this take. — Preceding unsigned comment added by Amingilani (talk • contribs) 15:49, 30 June 2019 (UTC)

Semi-protected edit request on 15 September 2019

Request to change the value of planck's constant in the article to the new exact definition of h=6.62607015e-34 Js or to include an explanation as to why this is not the stated value in the article. The note"[9]" in the article even refers to a source giving the exact value which is correct. No standard uncertainty since its set as exact.Durrstopp (talk) 11:41, 15 September 2019 (UTC)

@Durrstopp: I've confirmed your account so you should be able to edit the page yourself now. Let me know if you are still having problems. SpinningSpark 13:36, 15 September 2019 (UTC)

History and discovery

"For most of history, only visible light was known"?

Need to clarify what is meant by "known". Perhaps replace "known" with "characterized" because as long as there have been Homo Sapiens, we have experienced the direct effects of ultraviolet radiation (sunburn) and infrared radiation (using fires to keep warm). — Preceding unsigned comment added by 2600:8806:3400:3DB:C834:1C7:DB5F:C251 (talk) 22:44, 5 November 2019 (UTC)

High to low?

Color Wavelength interval Frequency interval
red ~ 625 to 740 nm ~ 480 to 405 THz
orange ~ 590 to 625 nm ~ 510 to 480 THz
yellow ~ 565 to 590 nm ~ 530 to 510 THz
green ~ 520 to 565 nm ~ 580 to 530 THz
cyan ~ 500 to 520 nm ~ 600 to 580 THz
blue ~ 430 to 500 nm ~ 700 to 600 THz
violet ~ 380 to 430 nm ~ 790 to 700 THz

Wouldn't it make more sense to have the colors in the wavelength/frequency chart near the bottom go from violet to red? Most electromagnetic charts go from high energy to low energy. Same with the page. D'Agosta 15:14, 9 August, 2005 (UTC)

  • I'm not certain which "chart" is referred to above, but the chart titled "Electromagnetic radiation interaction with matter" is certainly opposite of the other vertical charts in the article which all start at the high end (Gamma rays) and progress to the low end (radio waves). I've had users come to me in confusion, having to read this one chart upside down to follow the logic. Is there any reason it SHOULDN'T be flipped over? I'll await comments, then be bold.  :-) Thanks! WesT (talk) 22:55, 20 November 2019 (UTC)
    • @Westley Turner: That is a very old post and it is rarely worthwile replying to discussions that old. The user who posted it has not edited for over six years. This version of the article is nearest to the decades old post. The chart being referred to is probably the one I have posted to the right here. It is no longer in the article. As a telecommunications engineer, we would naturally go from low frequency (low energy) to high frequency (high energy) in charts and graphs. But I don't have an axe to grind on this. SpinningSpark 12:03, 21 November 2019 (UTC)
      • Ah! Yes. That makes sense. I didn't have the time to look into it further. Thanks for the research. I may have time tomorrow, so I'll look at the old as well as the new and see if it really makes sense to swap the order of the current table of interactions, but as you say, the norm is to go from low to high...so would that entail reversing all the other charts/graphs on this page to match??? Thanks! (BTW I was about to start a new topic, but I saw that this OLD one fit, so I branched out from it in spite of its age.) WesT (talk) 00:10, 22 November 2019 (UTC)

The Electromagnetic-Spectrum.svg image is misleading

The spectrum diagram https://en.wikipedia.org/wiki/File:Electromagnetic-Spectrum.svg is very misleading due to the unfortunate placement of the horizontal lines around the label "Radio, TV", which suggests that the radio/TV spectrum extends only from 30MHz to 1GHz. These lines are probably intended to indicate just the portion that's expanded to the left. However that's not the main impression. Also, in terms of widely-known services that could usefully appear on the diagram, mobile phone frequencies would be a useful addition. Gwideman (talk) 19:36, 8 April 2020 (UTC)

Atmospheric electromagnetic opacity chart is incorrect

File:Atmospheric electromagnetic opacity (corrected longwave).svg

The original chart is incorrect (and it is even written beside the image). Below is my attempt to correct the file. Unfortunately, the wikipedia thumbnailer did not render the text above the LW part of the chart. No idea why. I used Inkscape to edit, which suggested to convert the original image from 90 DPI to 96, but I doubt that's what caused it. Anyway, the article is locked, so suggesting it here. — Preceding unsigned comment added by Anterat (talk • contribs) 08:01, 25 September 2020 (UTC)

@Anterat: The chart is not incorrect for what it claims to be showing – Earth to space opacity. How do you know your new chart is accurate at all wavelengths for terrestial communication. You seem to have just assumed that it is the same as Earth to space, which is somewhat unlikely. If that is correct, your work is original research and can't be used in the article. I requested the Graphics Lab some time ago to produce another diagram for Earth to Earth opacity, shown here. This is more detailed, but does not cover the entire spectrum so may not be so suitable for this article.
The reason the text is not rendering is that you have inserted it outside the language switching area for English. The Spanish and French annotations still show the long-wave region as blocked (as you can see if you try switching to them in the drop-menu on the image page). It appears to be treating your text as an undefined language. I would recommend you amend the text in Inkscape using the built in XML editor rather than graphically. That way you can be sure you are putting it in the right place. You should also amend the French and Spanish text in case the image gets used in another language. Also, you cannot claim copyright of this as only a small part of it is your own work. Derivative works should still be credited to the original authors and they still own the copyright in it. I've reported that problem on Commons, if you don't change the license fairly quickly it may get deleted. SpinningSpark 13:39, 26 September 2020 (UTC)

Ancient knowledge

"For most of history, visible light was the only known part of the electromagnetic spectrum", so says the opening sentence of the history section (it is also a direct copy from the source which is very naughty without attribution). This is a highly dubious claim. First of all, radiant heat was also known to the ancients. They could feel it every time they gathered round the fire or stepped out into the sun. More importantly, no one even suspected that light was electromagnetic in nature until Maxwell. "For most of history" no one knew there was such a thing as electromagnetism at all – until Oersted in 1820.

The source for this is a book published by iUniverse, a self-publishing house, by a scientifically unknown author (the introduction explicitly says he is not a scientist). That makes it an unreliable source for our purposes. I intend to remove this, perhaps replacing it with something more accurate, but I'll wait to see if anyone else has got a comment to make first. SpinningSpark 09:17, 14 November 2021 (UTC)

Good point. And I think the section would be fine without that first paragraph. Willondon (talk) 12:00, 14 November 2021 (UTC)
Good catch. I agree with adding infrared to visible light. It seems to me the first paragraph could just be edited to make it clear that until Maxwell scientists didn't have a correct theory of what these rays were; I think the paragraph is otherwise good and should be kept if it can be sourced. A lot of the physics of electromagnetic waves (optics) was learned before it was known exactly what light was. Newton originated the concept of a 'spectrum' in 1666 when he discovered white light could be divided into different wavelengths with a prism. I think that could be included too. --ChetvornoTALK 15:26, 14 November 2021 (UTC)
Done, and I've filled in a few other gaps as well. SpinningSpark 15:01, 15 November 2021 (UTC)

Scientific and Philosophic Objection Regarding upper limit for long wavelengths

Would it be better to simply say that the limit for long wavelengths is unknown/undefined/infinite rather than stating that a wavelength could be the size of the universe?

This comparison stopped me in my tracks trying to imagine such a wave... could it actually propagate? If so, where? How would one construct a device to detect a wave of that size? What size and shape would an antenna be? It surely couldn't be something like a "quarter-wave antenna". It would have to be a much smaller fraction.


Examples in the article:

"The limit for long wavelengths is the size of the universe itself, while it is thought that the short wavelength limit is in the vicinity of the Planck length.[4]"

to

"It is thought that the short wavelength limit is in the vicinity of the Planck length. [4]. The longest a wavelength can be hasn't yet been determined."


"...gamma rays have very short wavelengths that are fractions of the size of atoms, whereas wavelengths on the opposite end of the spectrum can be as long as the universe."

to

"...gamma rays have very short wavelengths that are fractions of the size of atoms. The opposite end of the spectrum [ED. nice place for that simile] ,the size of very long wavelengths, has yet to be determined."


I wanted to gather some input first, before making any changes, to see if anyone else has the same sort of scientific and/or philosophic objection to a Universe-sized wave...

AreThree (talk) 07:14, 21 January 2022 (UTC)

My first question is does the source actually say that? I can't access it. My second question is is it even true? Waves of that size would be limited to only those wavelengths that can exist inside a universe-sized cavity. Better just to say there is no known limit for long wavelengths. SpinningSpark 17:13, 21 January 2022 (UTC)
Agree. Even if the book does say it, I don’t know if it should be regarded as a RS on this subject. It’s just an engineering text. And I’ve come across errors in other books by this author. --ChetvornoTALK 18:49, 21 January 2022 (UTC)
Agree. If the universe had an overall net electric charge distributed uniformly throughout the universe, then the E field would have a DC component which would have essentially an infinite wavelength. Constant314 (talk) 19:03, 21 January 2022 (UTC)
There is really no way of knowing if the source says that or not, as the link (as seen from archive.org) goes to a google books page that is not all archived. I would have to find a physical copy. As Chetvorno said, there have been errors in other books from that author, I would think that a better source wouldn't be that hard to find.--AreThree (talk) 00:23, 22 January 2022 (UTC)
Searching IA using a URL that contains only the book ID is only ever going to get you the overview page. To find a book preview on IA (assuming that google even allow previews to be archived – I've never tried it) one would have to use a URL with a query specifying a page number, a search term, or both. The query terms would have to be exactly the same as those used by the person doing the archiving so it would be a lot of trial and error with probably no good result. I've found that these authors habitually reuse vast swathes of text in book after book. Since I've failed to find anything similar in their other books that's not looking good.
Getting the source information is not as difficult as you think it is. Wikipedia:WikiProject Resource Exchange/Resource Request are very good at getting information from inaccessible books and papers. As long as you don't ask for the entire book (a few pages to a whole chapter is the limit) they usually deliver in a few days. Clarifying my first comment, it's not difficult for you. Always remember that you are using the time of a volunteer librarian or student somewhere in the world to go and dig this up so don't make unnecessary requests. SpinningSpark 09:58, 22 January 2022 (UTC)
I've now edited "size of the universe" out of the page. SpinningSpark 10:26, 22 January 2022 (UTC)

Proposed merge of Spectral bands into Electromagnetic spectrum#Regions

same concept fgnievinski (talk) 04:45, 11 May 2022 (UTC)

  • Oppose, these absolutely are not the same thing. Region, in this article, refers to the largest designation of bands of the spectrum such as X-rays. Spectral bands refers to a group of closely spaced spectral lines. The former are universal definitions and each is a continuum. The latter are specific to the material or object emitting them and are consist of a collection of discrete wavelengths. SpinningSpark 11:42, 11 May 2022 (UTC)
  • Strong oppose for the same reason; these are very different concepts. I do hope that the spectral bands article gets expanded, because it's an important subject, but it's quite different from the general coverage of the EM spectrum. Mover of molehillsmove me 14:46, 26 August 2022 (UTC)
Closing, given the uncontested objection and no support. Klbrain (talk) 15:54, 21 September 2022 (UTC)

Shortest wavelength and Planck length

An IP tried to remove the claim that the shortest wavelength possible was related to the Planck length (and deeleted the ref which might have been referencing other parts of the para). Here is another source that make that claim;

There are many more, of varying degrees of authority on the subject. SpinningSpark 13:51, 2 October 2022 (UTC)

I don't believe that this assertion has any mainstream support. You'll see that the source you linked says "The possible missing element ...", and is is essentially saying that "if we assume some speculative condition, we might find that ...". In the currently accepted theoretical framework, a hard limit to the "maximum frequency of a photon" cannot be accommodated, so such speculation includes upending essentially all currently theories, and does not fit within them. To include any such statement (and this source is evident not an authority on quantum physics) in an article without giving the context would be silly. I suggest bringing this up at WT:PHYS if you want input from more knowledgeable people. As another note, this is essentially an article about classical electromagnetism, with barely a mention of photons. —Quondum 17:32, 3 October 2022 (UTC)
An introductory text on nanotechnology (which involves things on the scale of whole molecules) won't be a good source for anything about quantum gravity. That would be like trying to learn string theory out of a textbook on molecular biology. XOR'easter (talk) 15:41, 6 October 2022 (UTC)
Well put. The reliability of a source depends on context. Each source must be carefully weighed to judge whether it is reliable for the statement being made in the Wikipedia article and is an appropriate source for that content. Further, this source does not even seem to provide a reference, and so cannot be regarded as a secondary source.
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