Talk:Spectral radiance

Merge proposal

I have proposed a merge with Radiance, since spectral radiance is currently covered in that article. I am not sure whether it would be best to merge Specific radiative intensity into Radiance, or whether the material on spectral radiance in the Radiance article should be split out and merged with this article to form a new article, Spectral radiance. Note that spectral radiance seems to be a broader term than specific radiative intensity, since spectral radiance can be in either frequency or wavelength units, while this article only mentions frequency units for specific radiative intensity.--Srleffler (talk) 05:45, 14 May 2010 (UTC)

There is a diversity of approaches to electromagnetic radiative studies, with a corresponding diversity of terminologies. There are perhaps two partly different approaches to radiometry, that of the practical characters, and that of the theoretical characters. The difference comes clearly into play when it comes to defining radiative flux (density). I am not quite up to that yet. The difference in definitions is partly due to the need of theoreticians to have a terminology that can conveniently be developed in mathematical terms, with logical consistency and coherence with other branches of physics. The radiance article is perhaps tending to be written more from the practical viewpoint. Other relevant articles are on radiometry, intensity (heat transfer), thermal radiation, light, Poynting vector, and others. It is not immediately obvious to me how to assemble these things. This is a work in progress.Chjoaygame (talk) 06:25, 15 May 2010 (UTC)

I'm not completely clear on how best to organize the material either. Keep in mind that Wikipedia articles are organized by subject, not by terminology. Different terms for the same thing (or sometimes closely related things) are covered in a single article. Conversely, distinct uses of the same term are covered in separate articles. Spectral radiance and specific radiative intensity seem to be essentially the same thing, so they need to be covered in a single article. What we need to decide is whether it would be best to cover them at Radiance or in a new article Spectral radiance, or perhaps here at Specific radiative intensity. I would prefer the first or second option, since I think spectral radiance is a broader term than specific radiative intensity, and it fits better with the other radiometry articles.--Srleffler (talk) 15:23, 15 May 2010 (UTC)

As I look at the article on radiance, it is not clear to me whether radiance is a description of the field, which should have a value at every point of the three-space-and-one-time-dimensional field, or whether it refers only, as the article seems to say, to particular areas of particular surfaces. The article on radiance does not give references to make this clear. The article on radiance does say "see also etendue". The latter gives some idea of the geometry, and perhaps should be included in the present discussion. So, probably, should Intensity (heat transfer) and radiative transfer.Chjoaygame (talk) 07:21, 16 May 2010 (UTC)

The surface need not be a real physical surface; the radiance is a description of the field, valid at any point in space.--Srleffler (talk) 04:00, 10 September 2010 (UTC)

The fact that radiance has developed more or less independently in computer graphics and physics should not be a reason for having two articles on the same concept. I suggest merging this article with radiance (since the latter is more than six years older) and generalizing the point of view of the latter so that it's less specific to light. For the latter I took a small step just now with a number of edits aimed at making it less light-specific as well as making the connection with black body emission. --Vaughan Pratt (talk) 20:15, 9 October 2011 (UTC)

Terminology

The term specific intensity is used in the classic works on radiation such as Planck 1914, and many other authoritative physics texts. That was the reason for introducing this article; that reason has nothing to do with computer graphics. The classic authorities actually speak of specific intensity without the qualifier radiative because they are writing in a radiative context.

As for seniority, one could ask 'seniority of what?' Seniority of Wikipedia entry or seniority of material? Does the Wikipedia have a policy of authority for seniority of Wikipedia entry? The term specific intensity is over a century old. The term radiance is an update "improvement" promulgated by authority of committees and is the product of committees.

Paltridge and Platt comment: "Even basic quantities such as radiant flux and radiant intensity as used in the general literature are not often the same as the formally endorsed definitions of those terms."

So far as I understand it, the function of the Wikipedia is to collect and report and make accessible findings from reliable sources, which are many and various in this case. So far as I understand it, it is not to act as a thought-police to enforce exclusive conformity the recommendations of committees, which are only one kind of reliable source, and not to try to regulate diversity of viewpoint, and not to try to enforce conformity to the one and only true and correct and errorless and completely general doctrine and point of view and form of language.

According to Born and Wolf and to Hapke, the terms (spectral) brightness and specific intensity and spectral radiance mean the same thing. They refer to a field quantity per unit frequency or wavelength, per unit area, per unit solid angles. They refer to a fileld of non-collimated light. They are different from irradiance and from (light) intensity, which both have the dimension of energy flux density per unit area. Intensity refers to a beam of collimated light. Irradiance refers to non-collimated light immediately originating from a specified surface per unit area of view from a specified direction.

The reason for the qualifier specific is to make the term apply to uncollimated non-blackbody radiation as well as to blackbody radiation, and to provide for solid angle.

The term (light) intensity by itself is sometimes (Born and Wolf 1999) used to refer to the intensity of a collimated beam. This is also called the irradiance.

The specific intensity of a thermal radiative field is non-zero because it is per unit solid angle, while the (integral) flux in any exactly specified direction is infinitesimal and unmeasurable as such. The intensity of a collimated beam is not infinitesimal and is measurable as such, because it is in the exactly specified direction of the beam.

Born and Wolf comment: "It is unfortunate that the same word is used to denote two different quantities."

The term brightness is currently defined in its Wikipedia article with the source given as the ordinary language dictionary of Webster. A different definition is given in the Oxford English dictionary but is not cited by the Wikipedia article. No opinion is offered by that Wikipedia article as to the relative reliabilities of those two sources. The Wikipedia article on brightness currently does not have much to say about brightness referring to specific radiative intensity, apart from offering opinions about what is "correct" according to the US government. In the latter opinion, it seems from the Wikipedia article that brightness is currently opined as a term of psychophysics, not of the physics of matter. Perhaps someone will feel like remedying this.

As for specificity for light, the terms discussed in the present articles in general refer to all wavelengths of electromagnetic radiation, not just to the visible wavelengths. Some authors regard the term light as referring to all wavelengths, not only to the visible.

References

Chjoaygame (talk) 23:01, 9 October 2011 (UTC)

The term radiance is an update "improvement" promulgated by authority of committees and is the product of committees. Decisions about Wikipedia articles have to be made somehow. What alternative are you proposing to decision by committee? The alternative you've proposed at Talk:Planck's law is to omit material calling for a decision. --Vaughan Pratt (talk) 08:11, 12 October 2011 (UTC)

Dear Vaughan Pratt, you seem intent on putting thoughts into my mouth. I do not see the need for a decision in this case. You are demanding one here, and telling me what I've proposed elsewhere; there I didn't propose, as you allege, omitting material, just putting in a different place from the one you favour. Wikipedia editing decisions are made by Wikipedia editors, not by committees.Chjoaygame (talk) 08:19, 12 October 2011 (UTC)

Citation overkill

This article has serious citation overkill problems. Larryisgood (talk) 14:21, 20 August 2011 (UTC)

Requested move 8 October 2022

The following is a closed discussion of a requested move. Please do not modify it. Subsequent comments should be made in a new section on the talk page. Editors desiring to contest the closing decision should consider a move review after discussing it on the closer's talk page. No further edits should be made to this discussion.

The result of the move request was: moved. Given that there was no participation in 25 days while the discussion was open, this is considered as non-controversial technical request. Yet, in case of someone requesting a page-move again, it should go through requested moves process. Splitting the article is outside the territory of move discussion. Given the inactivity on this talkpage, it is recommended to initiate a discussion on the relevant wikiproject to discuss/decide what content should be kept/split. Regards, —usernamekiran (talk) 10:58, 3 November 2022 (UTC)

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Specific radiative intensity → Spectral radiance – The intro defines "spectral radiance" as the more modern term. As part of the move, we should split Radiance, moving content pertaining to spectral radiance to this article. Srleffler (talk) 22:50, 8 October 2022 (UTC) — Relisting. Sennecaster (Chat) 05:25, 16 October 2022 (UTC) — Relisting. — Ceso femmuin mbolgaig mbung, mellohi! (投稿) 23:44, 26 October 2022 (UTC)

Relisting comment: Still no participants yet; one more try. — Ceso femmuin mbolgaig mbung, mellohi! (投稿) 23:44, 26 October 2022 (UTC)

The discussion above is closed. Please do not modify it. Subsequent comments should be made on the appropriate discussion page. No further edits should be made to this discussion.

• Note: the requested target, "Spectral radiance" was a redirect to Radiance. So before the page move, I updated all the "Spectral radiance" links to "Radiance" (example edit). After the move, "Specific radiative intensity" redirects to "Spectral radiance". —usernamekiran (talk) 11:35, 3 November 2022 (UTC)

eV

I suspect that some use per unit energy, instead of wavelength or frequency. (Physics likes eV.) Should this be mentioned? Gah4 (talk) 23:43, 16 June 2023 (UTC)

Not based only on suspicion.--Srleffler (talk) 06:42, 17 June 2023 (UTC)