Talk:Huygens–Fresnel principle

message: A bit of a crap description, in  my view at least. Put simply, Huygen's Principle is that a wave front can be thought of as infinite amount of point sources that produce spherical disturbances that reinforce to produce the secondary wavefront and so on. Although the author mentions how it is related to diffraction, he/she fails to explain how in any significant depth. I feel that too many people on Wikipedia (as brilliant a resource as it is) try to sound clever by using fancy language which at most times is inappropriate. (posted anonymously, 21:21, 2 June 2005 129.67.48.245) 
=== Be more specific in your critique ===
Actually I found this explanation fine, and I find Wikipedia to be a good resource in addition to others.
Although I understand your complaint in general, as this does happen (see next paragraph), you yourself did not add any value at all to the definition, nor go into even a decent level of detail on expanding the problems you had with it.  Simplicity is good; but you still have to be artful in getting your point across.  You didn't imho.
To add your own perspective is fine, but to blurt a brief complaint that has no depth or richness itself, frankly just makes you appear as actually the very kind of person that exploits what nominal personal knowledge you have on a subject for reasons of poor self-confidence.
Try to add useful criticisms with some depth instead of coming off, shall we say, a bit unpleasant?
mmf 06:30, 8 November 2005 (UTC)
replies: text: FWIW, I think the description (as of Jul 2007) is really rather good. ErkDemon 17:23, 27 July 2007 (UTC)
thread_title: Criticism

message: Actually I found this explanation fine, and I find Wikipedia to be a good resource in addition to others.
Although I understand your complaint in general, as this does happen (see next paragraph), you yourself did not add any value at all to the definition, nor go into even a decent level of detail on expanding the problems you had with it.  Simplicity is good; but you still have to be artful in getting your point across.  You didn't imho.
To add your own perspective is fine, but to blurt a brief complaint that has no depth or richness itself, frankly just makes you appear as actually the very kind of person that exploits what nominal personal knowledge you have on a subject for reasons of poor self-confidence.
Try to add useful criticisms with some depth instead of coming off, shall we say, a bit unpleasant?
mmf 06:30, 8 November 2005 (UTC)
replies: text: FWIW, I think the description (as of Jul 2007) is really rather good. ErkDemon 17:23, 27 July 2007 (UTC)
thread_title:  Be more specific in your critique 

message: I recently added a short section on the connection between Huygens Principle and the Greens function method. For classical and modern physics, the Huygens Principle and its connection to the Greens Function method is tremendously important. A good reference is The Mathematical Theory of Huygens' Principle (Paperback) by Bevan B. Baker, E. T. Copson. The section was removed without explanation. I do not want to add it again without discussion. Best, Rb
I didn't actually remove it, I integrated it into the previous section.  I agree the connection is really important, and I'm glad you brought it up, I just think the current version reads easier.  It seemed strange to have a separate section for 2 or 3 sentences.  If you plan on expounding, by all means readd it.--Hyandat 19:57, 20 December 2005 (UTC)
thread_title:  Query 

message: Shouldn't it be Huygens-Fresnel principle? Huygens' Principle makes sense, but when compounded the possessive should be on either both names (awkward, probably Huygens' and Fresnel's principle), or neither (the Huygens-Fresnel principle). If this is actually a "Fresnel principle" that belongs to Huygens, then the hyphen is wrong (Huygens' Fresnel principle). I'm not correcting this because I don't know the correct expression. edgarde 20:42, 5 June 2006 (UTC)
replies: text: Nope its Huygens-Fresnel Principle, I spent 2 months studying it at university! Rob.derosa 12:19, 25 June 2006 (UTC)

text: Thanks for fixing this. edgarde 06:10, 7 July 2006 (UTC)
thread_title:  Apostrophe or Hyphen has got to go 

message: [note by Siward de Groot:
i do not agree with the claim that "the same is true of light passing the edge of an obstacle", because if light passes a narrow slit in vacuum, it causes diffraction bands, but there is no matter in the slit to act as secondary source of light.
Rather, the explanation in this case is that:
if an (infinitely large) metal screen is between a source of light and a white wall,
then there will be no light falling on the wall.
This is because the electromagnetic force of the light acts on the wall, and it also acts on the metal shield, where it gives rise to a secondary  electromagnetic force, that is the exact opposite of the original stimulus, so that on the light side of the screen reflected light is apparent, while on the wall side of the screen primary and secondary forces cancel out, so it is dark there.
The secundary force is due to the combined effect of all atoms of the screen.
Now if a slit is made in this screen,
all parts of this screen still experience the same primary stimulus, and therefore produce the same secondary response, except for the atoms that previously were where now the slit is.
Thus the resulting lightness on the wall equals the secondary emission previously caused by these atoms, multiplied by -1 , for every point in time.
It is for this reason that the amplitude of the light apparent on that wall can be computed as if it were caused by secondary sources of light in the slit.]
Moved by --Hyandat 17:52, 23 July 2006 (UTC)
thread_title:  di Groot's comment 

message: Enormousdude, this section you're editing has more fundamental problems.  First the Psi(r) should not be a function of r, but of the field location where you want the result (call it x or something); the r gets integrated out.  Second, the integral assumes the functions add up all in the same direction, omitting the cos(theta) that Joe Goodman shows, here on page 66.  Perhaps that's why it's a far-field approximation?  It's not because all the points in the aperture are in phase; that works for near-field just as well, I think.  How it becomes a Fourier transform is not explained at all; it comes from the x ocations off axis corresponding to gradients in r that through the exponential make the varying-frequency sinusoids.  So you need to say something about how the r pattern depends on the field location x to get from far-field approximation to Fourier transform.  The r in the denominator has negligible variation in the far field, which is why you end up with just the FT of the aperture shape.  Dicklyon 00:30, 21 June 2007 (UTC)
thread_title: Fourier transforms

message: As I understand it, the circular wavefronts coming from the infinity of points have different amplitude in different directions. In particular, if they have an amplitude of 1 in the forward direction it will be 0 in the reverse direction and in general have an amplitude of (1 + \cos\theta)/2. 155.212.242.34 (talk) 20:49, 7 December 2007 (UTC)
thread_title:  Direction dependance 

message: I am thinking about putting Max Born's book Principles of Optics: Electromagnetic Theory of Propagation, Interference and Diffraction of Light under a new reference section because the book offers some good explanations about Huygens-Fresnel Principle. Bchen4 15:38, 5 March 2008 (UTC)
replies: text: I added a references section.  But don't just add the book there; use it to add or support something in the article, and put it in a footnote.  Let us know if you need help. Dicklyon (talk) 16:14, 5 March 2008 (UTC)
thread_title:  Reference 

message: I beleive that most of what is in this article is either in, or should be in the diffraction article. Epzcaw (talk) 20:35, 29 May 2008 (UTC)
replies: text: That may be so.  But a separate article on this principle still makes sense, especially since it's so useful in general optical problems, as a way to explain rays, Snell's law, etc., not just diffraction. Dicklyon (talk) 20:58, 29 May 2008 (UTC)

text: No, there's no problem with diffraction.  My point is that the H-F principle also explains the normal straight-line propagation of light, the reflection and refraction of rays, and stuff like that that is not generally considered under "diffraction".  Huygens even used it to explain the anomalous refraction of Iceland spar. Dicklyon (talk) 00:07, 31 May 2008 (UTC)
thread_title:  Merge with diffraction 

message: The term "wavefront" is not at all well defined.
3piecesuits (talk) 16:11, 10 November 2008 (UTC)
thread_title:  Wavefronts 

message: The Huygen-Fresnel principle might well now be a "method of analysis" but it is also a fundamental building block of classical wave theory, to state "Huygens principle follows formally from the fundamental postulate of quantum electrodynamics" is chronologically misleading in the extreme, the principle itself can be used to derive Snell's law and this was fundamentally important to the wide acceptance of a wave theory of light pre wave-particle duality. Whilst reformulating all physics as following from quantum theory is commedable it is hardly helpful when people wish to investigate a more historical evolution. Perhaps acknowledging its historical uses as well as its modern applications would be appropriate considering the number of people who use wikipedia as a resource for rather lower level work than fourier optics?  —Preceding unsigned comment added by 144.173.54.122 (talk) 16:25, 18 March 2009 (UTC)
thread_title:  Classical wave theory approach  

message: I have expanded the article to include detail about Huygen's work, and Fresnel's development of it.  I have also explained the limitations of the Huygens-Fresnel principle - it is not very satisfactory, as it involves several arbitrary assumptions and an undefined inclination factor.  I have also included the theory behind the principle; this is based closely (but not exactly!)on Born & Wolf's treatment.
I have removed the sentence about its elegance, as I don't think that this can be applied to it.  Obviously, it was very clever in its time, but I think the accoldate should go to Kirchoff's diffraction formula, which does not appear anywhere in Wikipedia at the moment.  I hope to rectify this soon.  Epzcaw (talk) 17:27, 20 April 2011 (UTC)
thread_title:  Expansion of article 

message: I reverted a couple of recent edits that were mostly about putting LaTeX math mode into sentences.  This is generally frowned on.  Use ordinary html, or even better, the Template:Math version, which looks good in sentences but uses the same font as math.  Also there were changes to the use of the term "amplitude"; it's used in two ways, but I don't think the fix was great.  I'd keep amplitude for the U factor and use something else for the instantaneous wave value.  Dicklyon (talk) 23:59, 22 April 2011 (UTC)
replies: text: Yes, but amplitude can be complex; it's not just a magnitude.  Dicklyon (talk) 16:58, 23 April 2011 (UTC)
replies: text: I don't want to get into this argument again - what's in a name?.  So just refer to the absolute value of the complex amplitude as the 'magnitude'.  The disturbance can become 'amplitude' again, or it can stay as 'disturbance' to avoid confusion to those people who consider the amplitude to mean the magnitude as explained in this Wikipedia article. The latter he been implemented below. Epzcaw (talk) 19:01, 23 April 2011 (UTC)
replies: text: Have put 'magnitude' instead of 'amplitude' where relevant, anc 'complex amplitude' also where relevant.  I hope that this is non-controversial.  Epzcaw (talk) 15:33, 24 April 2011 (UTC)
replies: text: Good job.  Dicklyon (talk) 15:48, 24 April 2011 (UTC)
thread_title:  Reverted 

message: Removed text in italics
(which in most cases is true - as was found later - due to superposition (=addition, or interference) of all primary, secondary, tretiary, etc waves)
These assumptions have obvious physical foundation
Longhurst – “It is not made clear in the theory why the secondary sources produce  no effect in the reverse direction”
Fresnel (not Huygens) was indeed able to predict the many aspects of wave propagation but only with the addition of arbitrary assumptions with no physical foundation 
Born and Wolf: “The additional assumptions must, however, be regarded as a purley convenient way of interpreting the mathematical expressions, and as being devoid of physical significance”
I see no basis for the assumption that all waves propagate in a uniform sphere due to the "isotropy" of space. The only type of wave source which would propagate spherically would be an explosion, and that would only be due to multiple sources propagating simultaneously from the same point in all directions. The  wave creating mechanisms, compression and rarefaction occur due to linear motions in some specific single direction. This is not something that would ever produce a uniform, symmetrical, spherical disturbance in all directions.   — Preceding unsigned comment added by 107.77.199.210 (talk) 12:08, 20 July 2018 (UTC)
thread_title:  Removal of recent additions which appear to contradict reference sources - and no references provided 

message: Can anybody tell if Kirchhoff's diffraction formula implicates that the light or any other wave do travel backwards being π/2 < χ < π ? If that is the case that would be remarkable (not sure if that is the correct word) on the apropiate section (Mathematical expression of the principle). It would be useful if anybody could concretely state it, cause saying that "...however, K is not equal to zero at χ = π/2 " is not enough! . 
Also it should be stated, if that is the case, that Kirchhoff's diffraction formula is more exact than Huygens–Fresnel principle and dont leave it at reader's assumption. Thanks FranJH  — Preceding unsigned comment added by 201.231.51.236 (talk) 22:33, 18 November 2012 (UTC)
thread_title:  Quest II 

message: Does/should it have a wikipage? Or is it the same thing as the H-F principle? The former is mentioned in , p. 22 JMP EAX (talk) 14:26, 16 August 2014 (UTC)
thread_title:  [[Huygens’ principle]] (geometrical optics) 

message: Add some examples of how the average man might see the effects in real life. Jidanni (talk) 03:30, 8 November 2015 (UTC)
replies: text: Take a laser pointer and shine it on the edge of a razor blade, in a darkened room. Observe interference pattern on wall.  Go to a port with a long breakwater, and observe the wave. Spend a half-hour or a few hours looking and thinking. Pick a nice day so that its pleasant. 67.198.37.16 (talk) 19:18, 16 January 2016 (UTC)
thread_title:  Examples 

message: In 1900, Jacques Hadamard observed that Huygens principle was broken in even numbers of spatial dimensions.  This article should at least mention this. He then developed some conjectures regarding the solution to the wave equation that are still being grappled with today. See:arxiv and google 67.198.37.16 (talk) 19:22, 16 January 2016 (UTC)
replies: text: I just added a short two sentence remark to that effect. This paper: Huygens principle gives an excellent introduction to Huygens principle and this WP article would be greatly improved by following its general outline and presentation! 67.198.37.16 (talk) 19:47, 16 January 2016 (UTC)
replies: text: This also has a long long discussion reviewing many relevant references: Huygens principle works only in odd spatial dimensions. 67.198.37.16 (talk) 20:28, 16 January 2016 (UTC)
thread_title:  Hadamard's conjecture. 

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thread_title:  External links modified (January 2018) 

message: This is what I removed: 
The source further states though, "However, Schwartz was expressing the classical (i.e., late 19th century) view of electromagnetism. The propagation of light in quantum field theory actually is consistent with the very interpretation of Huygens’ principle that Schwartz regarded as nonsense."
This statement is debatable, and is an opinion of the writer of the article and not even of Schwartz https://en.wikipedia.org/wiki/Wikipedia:No_original_research
I doubt that a nobel prize in QFT as Schwartz does not have in mind first hand the QFT issues with wave/particle propagation in vacuum
:
:In case anyone want it, the reference is here.. Gah4 (talk) 02:45, 13 March 2022 (UTC)
thread_title:  Removed a statement based on opinions 

message: Hope this clarify the dilemma in this article between QED centric discussions and classical Optics related ones  — Preceding unsigned comment added by Flyredeagle (talk • contribs) 16:23, 3 July 2020 (UTC)
thread_title: Separated out Generalized Huygens principle 

message: The article says "Lisle had observed this fifty years earlier [than Arago]" but our article for Arago spot has sources that say Joseph-Nicolas Delisle and Giacomo F. Maraldi independently observed it nearly a century before, not fifty years. Jason Quinn (talk) 15:16, 12 March 2022 (UTC)
thread_title:  First observed when?