Talk:Electromagnetic spectrum

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Date	Process	Result
February 16, 2008	Peer review	Reviewed

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Reversed numbers?

Why didn't anyone notice the MIR and FIR values for Photon eV is reversed. Wrong numbers in the table. 65.36.54.181 (talk) 13:01, 19 December 2023 (UTC)[reply]

They do not look reversed to me.--Srleffler (talk) 06:07, 20 December 2023 (UTC)[reply]

Use frequency in discussions of energy.

I just stumbled upon the UV section: lots of "short wavelength" discussion. I encourage editors to avoid using "wavelength" in any sentence here about energy. Energy is proportional to frequency. Using the inversely proportional wavelength is unnecessarily confusing and physically not helpful. Johnjbarton (talk) 21:30, 27 January 2024 (UTC)[reply]

Is the 'Energy per Photon' correct for LF, VF and ULF radio frequencies correct?

I don't believe the 'Energy per Photon' is in correct units for LF, VLF and ULF radio waves. For example, LF has a frequency of 30 kHz, and yet it has 'Energy per Photon' of 124 PeV (petavolts). Photon energy should to down as the frequency goes down, yet here it suddenly takes a leap upward. Gary Bellerose (talk) 19:39, 31 August 2024 (UTC)[reply]

peV = pico electronvolt Constant314 (talk) 20:34, 31 August 2024 (UTC)[reply]

ah, I misinterpreted it. Thank you! 24.193.151.211 (talk) 20:36, 31 August 2024 (UTC)[reply]

That could have happened to anybody. Constant314 (talk) 20:38, 31 August 2024 (UTC)[reply]

😆 24.193.151.211 (talk) 20:40, 31 August 2024 (UTC)[reply]

Is peV even a thing? I think the table would be more informative without such abbreviations. Johnjbarton (talk) 14:55, 1 September 2024 (UTC)[reply]

I obviously totally agree, as someone who was confused by the abbreviations. Gary Bellerose (talk) 14:58, 1 September 2024 (UTC)[reply]

eV electron volts are very common units of energy in particle physics. 1 eV equals the work needed to push one electron against a potential difference of 1 volt. I added a note to the table. Constant314 (talk) 18:32, 1 September 2024 (UTC)[reply]

I removed the note. The units are given explicitly in each entry in the table, and the first one is linked. There is no need for a footnote saying what the units are. The OP's issue seemed to be lack of familiarity with p for pico, not lack of familiarity with eV.--Srleffler (talk) 19:59, 1 September 2024 (UTC)[reply]

The units are all given as abbreviations. The manual is ambiguous on how to handle this case. Maybe append to the table "Energy in electron volts (eV), with prefixes kilo-keV, milli-meV, micro-, nano-neV, pico-peV, and femto-feV." Johnjbarton (talk) 19:10, 2 September 2024 (UTC)[reply]

I'm not sure what the issue is. There is a link to electron volts earlier in the article, and the unit symbol "eV" is used prior to the table as well. I don't see a problem that needs to be solved. I do notice that the other units have links for each abbreviation to the unit's article. I'll do that for eV as well.--Srleffler (talk) 19:26, 2 September 2024 (UTC)[reply]

The issue is that two readers did not understand the abbreviation "peV". Johnjbarton (talk) 19:42, 2 September 2024 (UTC)[reply]

It may be better now that peV is a link.--Srleffler (talk) 19:44, 2 September 2024 (UTC)[reply]

I am one of the users who did not understand "peV" (as opposed to PeV). Not to drag this out too much, but the grid linked to by peV is just a comparison of relative energies. It shows an entry for '2 PeV' but no reference to peV and no explanation of what these respective abbreviations mean or what their scale is.

My suggestion would be to add a second grid listing the abbreviations, their full name, and scale. Just for us non-physicists :-). 24.193.151.211 (talk) 20:24, 2 September 2024 (UTC)[reply]

I've added such a table as a collapsible table. If anyone has any objections let me know and I'll remove it. I think it is helpful, perhaps not everyone agrees... Gary Bellerose (talk) 21:20, 2 September 2024 (UTC)[reply]

Let me introduce you to Template:Val. It will make the numbers in your table look better. Constant314 (talk) 22:31, 2 September 2024 (UTC)[reply]

Thank you, I will try that. I see someone has made it optional to view, excellent. Gary Bellerose (talk) 22:37, 2 September 2024 (UTC)[reply]

I can't see the table in edit mode now, not sure how to get to it... Gary Bellerose (talk) 22:44, 2 September 2024 (UTC)[reply]

@Gary Bellerose search for "Explanation of units and prefixes". I guess you are missing it because it is inside the spectrum table. Johnjbarton (talk) 23:32, 2 September 2024 (UTC)[reply]

I can see the table unless I'm in edit mode, where I can only see the headers of the table but not the data. Still not sure how to get there. Can't pursue this any more tonight, but any guidance would be appreciated. Gary Bellerose (talk) 23:49, 2 September 2024 (UTC)[reply]

You may have to use the "Edit source" tab. Constant314 (talk) 01:05, 3 September 2024 (UTC)[reply]

Sub-spectrum?

(located in the regions section, the first big paragraph at the start of this section-"There are no precisely defined boundaries between...") what do they mean by rainbow being the sub-spectrum of visible light? WorldDiagram837 (talk) 02:35, 26 December 2024 (UTC)[reply]

I assume that "subspectrum" is only meant to somehow embed visible light in a larger spectrum, but that makes no sense. Anyway the phrase containing subspectrum does not belong in that sentence so I deleted it. Johnjbarton (talk) 04:18, 26 December 2024 (UTC)[reply]

also for the paragraph above the table (in the same "Regions" section) [The region of the spectrum where a particular observed electromagnetic radiation falls is reference frame-dependent (due to the Doppler shift for light),...] Does the Doppler shift only affect light(as stated) or any observed EM radiation? WorldDiagram837 (talk) 03:37, 27 December 2024 (UTC)[reply]

It affects all EM radiation. Constant314 (talk) 03:51, 27 December 2024 (UTC)[reply]

The sources in the section "Regions" are weak or non-existent and some of the material seems to be made up. For example, part of the paragraph that includes the material on Doppler shift claims that the CMB contains "photons were from Lyman series transitions" which is not true. Johnjbarton (talk) 14:52, 27 December 2024 (UTC)[reply]

The article waffles about X-ray vs gamma radiation, but the cited sources all say the same thing: these are physically indistinguishable and are characterized by their origin, electronic transitions vs nuclear transitions.

I rewrote the later parts of the section with better refs. Johnjbarton (talk) 17:07, 27 December 2024 (UTC)[reply]