Talk:Van Cittert–Zernike theorem

NPOV dispute
This article was tagged as NPOV, but there have been no comments in the talk page as to why this was done or what "specific issues ... are actionable within the content policies." If no one provides any reasons as to why the article was tagged NPOV, the NPOV tag will be removed as a drive-by tagging. --Splat (talk) 03:32, 14 February 2011 (UTC)
 * Since no one has provided any reasons as to why this article was tagged NPOV, I'm going to remove that tag. I also don't believe that the tone is inappropriate and haven't heard any reasons as to why it is, so I'm going to remove that tag, too.  I will admit, however, that the article is confusing and does not yet have enough inline citations. --Splat (talk) 04:35, 14 February 2011 (UTC)

Is the introductory section really correct?
The «The Van Cittert–Zernike theorem is a formula in coherence theory that states that under certain conditions the Fourier transform of the mutual coherence function of a distant, incoherent source is equal to its complex visibility.» sentence may be erroneous...

As indicated by the formula $$\Gamma_{12} (u,v,0) = \iint I(l,m) e^{-2\pi i(ul+vm)} \, dl \, dm $$ given in the first section just below the introduction and table of contents, and even though $$u$$, $$v$$, $$l$$, and $$m$$ are not defined (and some factors may be lacking), the VC-Z theorem claims that the mutual coherence of the electromagnetic field in two given points is proportional to the Fourier Transform of the intensity pattern of the source for an argument connected to the distance between these two points.

In other respects, the mutual coherence is proportional to the visibility (or contrast) of fringes that the two points would give if there were acting as Young hole sources.

The reference 4 and the reference [Goodman, Statistical Optics, Wiley 1985] define concepts and notations of statistical optics that is the basic background of this theorem. 78.223.9.117 (talk) 00:04, 12 June 2013 (UTC)

«This implies that the wavefront from an incoherent source will appear mostly coherent at large distances.» I think that a "wavefront" (of an optical or electromagnetic field) can only be defined for a monochromatic spatially coherent source, as a wavefront is an isophase surface of a deterministic electromagnetic field that have sinusoidal variation with time at a given and fixed frequency. A "wavefront" cannot be called coherent or incoherent or partly coherent; these terms apply to qualify a (primary or secondary) light source. (Partly coherent or incoherent sources give electromagnetic fields that are no-more fully deterministic but must be described with the help of stochastic functions theory and the use of first and second order statistic properties, with usually some assumptions about stationarity and ergodicity) 78.223.9.117 (talk) 22:59, 11 June 2013 (UTC)

Uppercase or lowercase "van"
Regarding by user, the literature seems to disagree and regularly uses lowercase van. See, for instance, It is clear from the literature that both the person and his theorem are usually spelled with lowercase, as it was done in this article ever since it was created. Clearly the literature consensus is lowercase van, and I think we should follow the literature. Comments welcome. - DVdm (talk) 16:30, 12 January 2022 (UTC)
 * Extract of page 188
 * Extract of page 306
 * Extract of page 236
 * Extract of page 767
 * Extract of page 16
 * (many more)
 * Yes, just leave it like it is in the literature, Wikipedia is not the place to innovate. Also, this is probably the least relevant thing that could be discussed about this article. Tercer (talk) 17:42, 12 January 2022 (UTC)
 * Indeed. I have restored the long-standing consensus version: - DVdm (talk) 18:02, 12 January 2022 (UTC)
 * Interesting. I don't know how this relates to region, language or publication, but there do seem to exist some style rules around this, e.g.  that suggest that it is context-specific.  172.82.46.13 (talk) 14:56, 28 January 2022 (UTC)
 * This is what the Dutch do: van (Dutch) (according to Wikipedia anyway).Orenburg1 (talk) 17:19, 12 March 2023 (UTC)
 * van Cittert is wrong. Van de Graaff (generator) is correct. Only Dutch people know how to write Dutch names in the right way ... as is confirmed by the reactions here. 2001:4C3C:4100:8F00:60D7:2C56:8958:86AB (talk) 13:30, 21 July 2024 (UTC)
 * For Wikipedia there is only one thing right. The literature. By design. - DVdm (talk) 15:50, 21 July 2024 (UTC)

Seems fine
The article seems fine to me. The topic is confusing, but this discourse follows the lines of Chapter 14 of "Interferometry and Synthesis in Radio Astronomy" by AR Thompson, JM Moran, and GW Swenson Jr. Might as well just copy that chapter. For me, the three key items are 1) Understand what it means for an electric field to be coherent; 2) The idea of the strength of the electric field at the two points of the observation plane becomes nearly identical if one is far enough away from the source, but that the difference in path length as it affects the phase of each of the two points on the observation plane must not be neglected, but can be simplified taking advantage of the large distance involved; and finally 3) the electric field at the two points on the observation plane only come from each point on the source individually and not combined with multiple points on the source as they are uncorrelated and will wash out. As stated in 1954 by Hanbury Brown and Twiss in their paper describing intensity interferometry, "It was shown in §2 that the ' Michelson ' interferometer can be analysed by considering the radiation at a single frequency from a single point in the source. The interaction of radiation from different points in the source or of signals at different frequencies can be neglected, since, as long as they are uncorrelated, they contribute nothing to the average value of the output. Ref: Hanbury Brown and Twiss, 1954, The philosophical magazine. LXXIV. A new type of interferometer for use in radio astronomy.45, 663.

BTW - the link to the video is broken and should be removed. — Preceding unsigned comment added by Tmozdzen (talk • contribs) 19:19, 15 February 2022 (UTC)

bandwidth
The term 'bandwidth' is used in this article, and it means the bandwidth of a band-pass filter. However, the link from it takes the reader to the 'bandwidth' of a banded matrix, which is an unrelated concept. The link should rather point to

https://en.wikipedia.org/wiki/Band-pass_filter 105.186.176.229 (talk) 18:20, 28 February 2023 (UTC)

Dutch names
Only the external link uses the right name: with a capital letter V. Weaky3 (talk) 13:18, 18 March 2023 (UTC)
 * His father's name was spelled with lowercase v:
 * Extract of page 496
 * listing Benjamin Pieter van Cittert being his father, and listing more names with lowercase vans: P. van den Ent and Jan van der Hoeven
 * For the theorom, the literature uses lowercase v:
 * Extract of page 188
 * Extract of page 306
 * Extract of page 236
 * Extract of page 767
 * Extract of page 16
 * Some Dutch names have a Van, some have a van. This one seems to have a van.
 * And, yes, the external link of almost every article on Wikipedia starts with a capital letter. See Letter,, House, , Etc, . - DVdm (talk) 14:01, 18 March 2023 (UTC)
 * Dutch names without a first name ALL start with a CAPITAL letter. Van Basten (capital V!!!) was a famous football player. But his full name is Marco van Basten (no capital v!!!). DVdm does not know what he is talking about. I am Dutch, he is not. This article is a very bad example of how English speaking people rape foreign languages. Yes, this makes me really angry. Weaky3 (talk) 23:37, 26 March 2023 (UTC)
 * EVEN WORSE, there is a Dutch link for this article with correct writing of the name!!!!! Why isn't DVdm refering to that link? Is hè personally involved in this, or what??? This should be general policy: first look for the link in the foreign language. Is that so hard to think of. It just shows a very one-directional mind of you all in these matters. Weaky3 (talk) 00:00, 27 March 2023 (UTC)
 * Not that this should matter, but I am Dutch, as I already explained at User talk:DVdm. What does matter, are the literature and policies and guidelines of the English Wikipedia, which is where you are finding yourself. If the literature spells the theorem with a lowerase case v, then Wikipedia spells it with a lowercase v. If the policies and guidelines of Wikipedia have consequences that make you angry, you might consider staying away from it. - DVdm (talk) 07:27, 27 March 2023 (UTC)
 * DVdm refering to non-Dutch authors how to write Dutch is like one blind man asking another blind man to describe a painting by Van Gogh (capital V). There is only one meaningful reference: the Dutch version of this article. It is obvious that there is no policy on this. And if there is, it is wrong! Weaky3 (talk) 07:59, 27 March 2023 (UTC)
 * And today I've learned that in this matter DVdm has been playing his dirty tricks on another Dutchman (Koitus) too. Blocking him forever??? For what can you block anyone forever??? Is this Russia??? Weaky3 (talk) 20:11, 28 March 2023 (UTC)
 * Second level warning for wp:personal attacks at your talk page: . - DVdm (talk) 20:49, 28 March 2023 (UTC)