Misplaced Pages

Fresnel equations conventions

You've stated many times that you've seen "multiple conventions (not merely sign conventions)" for the Fresnel amplitude equations. At some point I'd like to try to add to the article the formulas, explaining all the different conventions and giving all the different formulas, hopefully so clearly that people don't keep changing it later. BUT, I've personally only seen one convention, where the sign of r being + if the electric field points the same direction for the incoming and reflected wave, etc. What are the other ones, what fields are they used, what books can I find them in?

I really enjoy trying to clear up confusing convention differences, for example I've written mathematical descriptions of opacity, Torque#Terminology, Gaussian units, this webpage etc. :-) Thanks! --Steve (talk) 19:20, 12 July 2010 (UTC)

As you know, one must choose which direction of the electric field components is considered to be positive. Besides this, though, you have to choose what you mean by "amplitude". Electromagnetic theory texts are likely to take "amplitude" as "electric field". In other contexts, though, it is common to use "amplitude" to refer to the square root of the intensity, and write the Fresnel equations in terms of this quantity. This is not a trivial difference: the relation between intensity and electric field depends on the index of refraction of the medium, which is different on the opposite sides of the interface. The square root of intensity obeys different relations than electric field amplitude does. You can find an example of this treatment in Siegman's book.

There is also a choice to make, of the plane in which the vectors are decomposed. If I recall correctly, some authors take components in the plane perpendicular to the direction of propagation, while others take components in the plane perpendicular to the interface. Both treatments have their merits. I think there is a brief discussion of this choice in McCleod's book on optical coatings.

Hope this helps get you started. Be sure to consult sources in more than one field, since usage may vary between them.--Srleffler (talk) 05:08, 13 July 2010 (UTC)

References

1. Siegman, Anthony E. (1986). Lasers. University Science Books. ISBN 0-935702-11-3.
2. Hugh Angus Macleod (2001). Thin-film optical filters (3 ed.). CRC. pp. 25–6. ISBN 9780750306881.

Ferroresonance

I'd hate to deprive the electric power engineering community of what has evolved into a nice concise article on the subject. I may be able to secure permission to use the article from the original copyright owners. I doubt that they would object if they could get a reference. If so, how are permissions cited? Can you point me to any examples?

--Rcdugan (talk) 03:31, 13 July 2010 (UTC)

See Misplaced Pages:Donating copyrighted materials for information on what is required to use previously published material verbatim. Everything on Misplaced Pages is licensed such that anyone can edit it and reuse it for any purpose, so we can only use material if the copyright owner is willing to allow such modification and re-use. Misplaced Pages's license requires attribution: every author's contribution to an article is recorded in that article's history log. If material were to be added verbatim from another source that would have to be explained in the edit comment so there is a record of the source.

Note that attribution is separate from references. Typically sources consulted in writing an article are cited in footnotes. You can see examples of this in many articles. In the case of material included verbatim, we would of course have a footnote citing the original source. --Srleffler (talk) 04:31, 13 July 2010 (UTC)

Historical facts, no puzzling rules for manipulation

You have my answer on my talk page. Please act by science and historical fact not by "rules" --Showasw (talk) 18:22, 21 July 2010 (UTC)

Thanks

For the information on Dzierzon. I added info on modern conference and his name used in its titled. Since the vote has been based on biased data, I believe the article should be moved back, what's your opinion? --MyMoloboaccount (talk) 23:02, 22 July 2010 (UTC) My account goes waaay back to 2005 or 2006, I had to change because of hacking but I am not sockpuppet of Serafin whoever that is. --MyMoloboaccount (talk) 00:49, 23 July 2010 (UTC)

Polarization (waves)

Re whether Polarization (disambiguation) should be in the See also section of the article Polarization (waves), please see WP:FURTHERDAB. 69.3.72.249 (talk) 04:25, 23 September 2010 (UTC)

The list of exceptions at WP:FURTHERDAB does not include a link in the see also section of an article, and for good reason. One does not do "further disambiguation" by putting a link in See also, way at the bottom of the article. If further disambiguation is needed on an article, one would put the link in a hatnote at the top of the article.

The see also section is for links to additional articles that are relevant to the subject of the article. Things that happen to share the same name but are otherwise unrelated are not relevant. If any of the links at Polarization were relevant to wave polarization, those articles should be linked to directly, not through a link to the dab page. --Srleffler (talk) 01:13, 24 September 2010 (UTC)

References vs. external links

Thank you for your comment. I answered on my talk page. Let's continue there or in the Lumen talk page if you disagree. --Pot (talk) 13:29, 6 October 2010 (UTC)

candelas vs lumens

Hi Srleffler:

Thank you for your cordial welcome, and the update on the definition of the candela.

My issue with the relation given for the candela (= lm/sr) in the table for Photometric Units is simply that it's derivative, not definitive. Anyone learning photometric units (like myself) will be driven crazy trying to infer a logical hierarchy from the table. The fact is, lumens require candelas for definition, but the converse is not true.

Clarion-g7 (talk) 07:39, 13 October 2010 (UTC)

Yes, one should not attempt to infer a logical hierarchy from that table; the relation given for candela is not definitive. It is, however, intuitive. Compare to Template:SI radiometry units. Luminous intensity is to luminous flux what radiant intensity is to radiant flux, and the units of radiant intensity are W/sr. Really, luminous flux is the more basic quantity, but for practical reasons the SI base unit is the unit of luminous intensity instead. The table does mention that candela is the base unit, and the linked article provides all the details.--Srleffler (talk) 11:17, 13 October 2010 (UTC)

I would say confusing, not intuitive. Photometric units are what they are. The comparison to radiometry units may be enticing, but is not definitive either. Just my humble opinion. Clarion-g7 (talk) 03:47, 14 October 2010 (UTC)

An advice.

Hi. You are my advisor, so I bother you again with a question. Please, have a look at a talk of mine and to my reply to PAR. I have written this reply interpreting the very bief PAR's reply as "do what you want and then go away" (my talk was after a very very long series of discussions in the same page, and I was new in them). Now I have the doubt that the phrase "go from there" instead meant "go on, continue from there", so it was not so unkind. You know, my English is perhaps sufficient to speak of technical arguments, much less for colloquial expressions. So, I need your help. How do you interpret PAR's reply? Because, of course, if I misinterpreted it, I must apologize with him. What do ou think about that? Many thanks in advance (you can reply here). --GianniG46 (talk) 11:08, 23 October 2010 (UTC)

You guessed right above: to do something and then "go from there" means to start out doing something, and then continue on in the direction that that leads you. PAR is encouraging you to start out by editing the article to the way you think it should be, and then see what happens and continue from there. He doesn't say it, but I'm guessing he has in mind that other editors will probably jump in and change what you wrote, so you'll want to try to work with them and arrive at a compromise. His message is not at all unkind, and in fact was meant as encouragement for you to edit the article.--Srleffler (talk) 15:18, 23 October 2010 (UTC)

I replied on the Temperature page, and apologized on his talk page. Many thanks. --GianniG46 (talk) 22:54, 24 October 2010 (UTC)

I am glad to have been able to help.--Srleffler (talk) 04:12, 26 October 2010 (UTC)

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Photonics

Just wondered if you might have a look at the entry on photonics - the research section seems very biased towards comms topics, but photonics is so much broader than this. What's your opinion? --Opticalgirl (talk) 10:47, 1 November 2010 (UTC)

Optical mesh network

Thanks for the welcome and feedback on my first article! Jflabourdette (talk) 00:47, 9 November 2010 (UTC)

oops!

Thanks! Gwen Gale (talk) 17:30, 26 November 2010 (UTC)

Photometry

Hi Leffler,

Thank you for notifying me of your reversion of my edits on Photometry (astronomy) and Photometry (optics). I can understand why you would want to make sure the articles are linked considering the relationship between the concepts they discuss. According to hatnote documentation, the 'About' template is the "main template for noting other uses" while 'See also' sections are used when the topic of another article is "related to that of the current article and already contains a self-explanatory parenthetical". Hatnotes, including 'About' hatnotes, are for disambiguating articles that have ambiguous titles or ambiguous redirects. There are no redirects involved in this case and the titles already include parenthetical disambiguators. If the parenthetical disambiguators are not sufficiently specific to disambiguate their topics from each other, the disambiguators should be changed so that they are sufficiently specific. If astronomers and optical scientists use the term "photometry" differently, why are the current disambiguators ambiguous? Anyone typing "Photometry" into the search bar is presented with both options in the drop-down menu, and anyone who presses 'enter' will be presented with both options on the disambiguation page. There is no reason that a user would be looking for "Photometry (optics)" and would instead end up at "Photometry (astronomy)" without knowing that both articles existed. Links to the other article included in the body of each article should be sufficient for users interested in both topics. Have I addressed the reason why you feel the hatnotes should be included?

Neelix (talk) 17:30, 4 December 2010 (UTC)

Sorry I didn't reply sooner. You make a good argument. My concern is mainly that people working in specialized fields are not always aware of alternate usages of the same terms in other (related) specialized fields. An astronomy student who is unaware of the use of the term in other areas of physics might end up at Photometry (optics) and be confused, because the usage of the term does not agree with that in her field. A link at the top of the article serves to prevent this possibility. While you're right that searching shouldn't bring someone to the wrong article, links can. An astronomer might well be reading optics articles and follow a link to the photometry article, not being aware that the term has a different meaning in traditional optics. --Srleffler (talk) 02:45, 10 December 2010 (UTC)

Template:Diagram needed 2 listed at Redirects for discussion

An editor has asked for a discussion to address the redirect Template:Diagram needed 2. Since you had some involvement with the Template:Diagram needed 2 redirect, you might want to participate in the redirect discussion (if you have not already done so). Kumioko (talk) 15:15, 15 December 2010 (UTC)

Template:DiagramNeeded 2 listed at Redirects for discussion

An editor has asked for a discussion to address the redirect Template:DiagramNeeded 2. Since you had some involvement with the Template:DiagramNeeded 2 redirect, you might want to participate in the redirect discussion (if you have not already done so). Kumioko (talk) 15:15, 15 December 2010 (UTC)

Merry Christmas!

Hey Srleffler, I just wanted to take some time to thank you with the help you've given me on laser and optic related articles. I hope you have a wonderful time this holiday season, and may the coming year be filled with joy! Zaereth (talk) 02:41, 23 December 2010 (UTC)

Thanks. Merry Christmas to you too!--Srleffler (talk) 06:21, 23 December 2010 (UTC)

Why

I noticed you said "Never link adjectives. Link to the noun form" as your reason to avoid a redirect. Why? I'd say never avoid appropriate redirects. Dicklyon (talk) 04:51, 2 January 2011 (UTC)

I'm generally a strong advocate of not avoiding redirects, but I feel that links should point to something that has the form of an article title (even if the page with that title does not exist or redirects elsewhere). WP:NAME forbids using adjectives as article names, so links to adjectives don't have the right form. I had thought this was a pretty clear implication of the policy until you asked, but perhaps it is more a matter of personal taste than I had thought.

In the case of ultrarelativistic, the adjective is not such a bad link target. In many other cases, though, adjectives just don't make good links; they are more likely to be ambiguous, and less likely to have a disambiguation page, since articles are not permitted to have adjectives as titles.--Srleffler (talk) 07:21, 2 January 2011 (UTC)

Yes, I think you over-interpreted "Adjective and verb forms should redirect to articles titled with the corresponding noun." Dicklyon (talk) 17:11, 2 January 2011 (UTC)

MM fibre

Hi
I've put a post on the discussion page for multimode fibre and I noticed you've been on there and might be in a position to answer my query - would you have the chance to glance at it? Also interested from a theoretical point of view anyway :)
Cheers
Chris Toomuchrockcankill (talk) 17:19, 13 January 2011 (UTC)

Plasma Ball

Hello Srleffler,
The link to my page Plasma Art, has been in the Misplaced Pages article Plasma Ball from December 14, 2006, without being considered as a form of self publicity, but as a contribution to the subject. My link, I repeat, has been on Misplaced Pages for 5 years, aimed at http://www.esnips.com. Two days ago I changed the link to another page, (Artelista), because the site http://www.esnips.com where I was staying my website (for free), has become an unethical publicity machine, which ignores its users. I do not understand why you deleted my link, but did not remove the other link also goes to another personal page that shows the work of Scott Bogard. Are you against artistic experimentation? , I guess that's not possible, considering that the plasma lamp is a technological object that Tesla invented and then was transformed into a work of art by Bill Parker and other artists, through painstaking research and experimentation, as I do with my work. Can you reconsider your attitude and act democratically, not as an SS officer? You probably consider the latter question is too hard, I'm sorry, but I'm an artist, not a diplomat.

Greetings,
SdgPlasmaArt SdgPlasmaArt —Preceding undated comment added 00:10, 30 January 2011 (UTC).

Thanks for your message. Misplaced Pages has a policy on conflicts of interest, which you can read at Misplaced Pages:Conflict of interest. Editors are strongly discouraged from inserting links to their own websites, regardless of the merits of the external site.

Besides the conflict of interest, I didn't feel that the link added sufficient value to the article. Our primary goal is making the encyclopedia as good as possible, not acting as a directory of web links. External links should be used only when they add significant value to the article, and only the best sites should be linked. Also, the text on your site is not in English. On the English Misplaced Pages, the guidelines for external links favour links to sites in English, as these will be of the most value to our readers. Sites in other languages should not be linked from the English Misplaced Pages unless there is an overriding reason to do so.--Srleffler (talk) 04:15, 30 January 2011 (UTC)

Laser link

Hello!

I've built a new website for National Laser Company (www.national-laser.com) and would like to get your thoughts about adding a link from your main Laser wiki to this site.

I'm hoping I can impose and ask you to take a look at our site and see if you think there is merit to adding a link.

Thanks for you consideration.

Best regards,

Dirk 80eddy

Dirk Cline

80eddy (talk) 02:36, 3 February 2011 (UTC)

You will not be able to link to your site from here. Misplaced Pages is not a web directory, and may not be used for promotion or advertising.--Srleffler (talk) 05:26, 3 February 2011 (UTC)

Divergence (disambiguation)

I don't think I understand by what reasoning you would file Beam divergence or Divergence problem under Science, but Divergence theorem under the See also section? In my opinion this makes anything under the See also more difficult to find, including Convergence, the most important link in that section. —Ruud 13:44, 12 February 2011 (UTC)

A disambiguation page is a navigation tool for sorting out links to articles on topics that can all be referred to by the same name. In this case that name is divergence. Beam divergence is commonly referred to just as divergence, so it goes in the main list. Nobody would refer to the divergence theorem as just divergence, so it doesn't go in the list. It's debatable whether it should appear on the page at all. Note also that the divergence that divergence theorem refers to is already on the list. Divergence problem is a less clear case. If you view it analogously to divergence theorem it clearly wouldn't belong. On the other hand, that article is probably the only article we have on the observed divergence between temperatures reconstructed from tree ring widths and temperatures measured directly. To the extent that the article is about that divergence, rather than about the problem, it might be considered to belong on the list.--Srleffler (talk) 15:41, 12 February 2011 (UTC)

By that reasoning divergent series wouldn't belong on the disambiguation page either. If you're going to be idealistic about this, then the links should be removed, not put under the See also section (making Convergence too hard too find). If you're going to be pragmatic and include the links, then they should just be listed directly under the appropriate section. I think the pragmatic approach would be the most useful to most readers here. —Ruud 22:14, 12 February 2011 (UTC)

Divergent series is a similar case to Divergence problem: there probably isn't an article on this sense of divergence itself, so the article divergent series serves in its stead. I would be fine with deleting all of the links in the See also section except Convergence (disambiguation), which absolutely belongs there (and not in the main list).--Srleffler (talk) 06:32, 13 February 2011 (UTC)

Proposed deletion of HF Spectral Occupancy Experiment

The article HF Spectral Occupancy Experiment has been proposed for deletion because of the following concern:

non-notable experiment, information should be dealt with in context of findings

While all contributions to Misplaced Pages are appreciated, content or articles may be deleted for any of several reasons.

You may prevent the proposed deletion by removing the {{proposed deletion/dated}} notice, but please explain why in your edit summary or on the article's talk page.

Please consider improving the article to address the issues raised. Removing {{proposed deletion/dated}} will stop the proposed deletion process, but other deletion processes exist. The speedy deletion process can result in deletion without discussion, and articles for deletion allows discussion to reach consensus for deletion. Sadads (talk) 13:47, 18 February 2011 (UTC)

Fiber Optic Test & Measurement

Hello Srleffler! I've been adding quite a bit of information about fiber optic test equipment etc. There is a surprising lack of info in Wikipedoa about this general area. I'm a scientist - engineer with 30 years of specialist experience in this area, so probably uniquely qualified to contribute. My apologies if I've made the occasional Misplaced Pages snafu. As for the company Kingfisher, it has been a real technical pioneer in this area, so deserves an honorable mention. The "other" 2 companies in this area, Exfo and JDSU, have a page each, so this just balances things out. Cheers, BR. — Preceding unsigned comment added by Bruce Elphinston Robertson (talk • contribs) 06:29, 21 February 2011 (UTC)

Thanks for replying. I certainly think you have a lot to contribute in an area that can use a lot of work. I don't have any opinion on whether Kingfisher should have an article. I was just concerned that you seemed to be promoting the company. If you work for them or are otherwise associated with the company, you must not write about them here. Otherwise, just try to remain neutral and balanced.

Links to pages advertising commercial products are usually not appropriate. In particular, you used links to Kingfisher product pages as references to support various points about fiberoptic test equipment. We generally require references to reliable sources (as defined on the linked page). There are rare circumstances where a link to a company page may be appropriate, usually when the article needs to discuss that company or its products specifically. (The rules for when non-reliable sources can be used are here.) In any event, the appearance of multiple references to a single company and its products in a short time is likely to result in removal of all references to that company, since it looks like the company is attempting to promote itself on Misplaced Pages, which is not allowed.--Srleffler (talk) 05:59, 22 February 2011 (UTC)

Bessel_beam

I much appreciate your recent changes to Bessel beam thank you. The lead is now much more readable --Senra (Talk) 16:37, 5 March 2011 (UTC)

WQA and the removal of citation templates

Hello, Srleffler. This message is being sent to inform you that there currently is a discussion at Misplaced Pages:Wikiquette alerts regarding an issue with which you may have been involved. Thank you.

The issue is at WP:WQA#user:Bzuk and the removal of citation templates. Thanks, Andy Dingley (talk) 14:04, 15 March 2011 (UTC)

Hey Srleffler,

I have a question. I'm not sure if you're the right person to ask, but I guess I have to start somewhere. I have an optical flat mirror which I purchased from Edmund Industrial Optics, and I was going to try to get a decent photo of it. Do you think it would be OK to use the certification of flatness as a backdrop, or would that be getting into copyright issues?

Also, Edmund has some pretty good info about coatings, located here. Could that be used as a reference for articles like thin-film optics or beamsplitter, or would that be too much like advertising? (I don't have any actual books on coatings.) Zaereth (talk) 22:33, 24 March 2011 (UTC)

I would be careful about using a certificate as a backdrop, both due to copyright and due to the desire not to promote products on Misplaced Pages. Certainly don't do it if the manufacturer's name or logo is visible. Purely functional things like a graph or chart or other data about the lens might be OK. Copyright protects artistic expression, not purely functional data.

I've seen other cases where technical material on a vendor website was used to good effect as a reference. There are a few requirements:

• You must not work for or otherwise be affiliated with Edmund (no conflict of interest)
• The site is not a reliable source, so if anybody challenges it it will likely be removed.
• If there is no challenge and the material seems good, use of such links should follow the rules at WP:SELFPUB:

1. the material is not unduly self-serving;
2. it does not involve claims about third parties;
3. it does not involve claims about events not directly related to the source;
4. there is no reasonable doubt as to its authenticity;
5. the article is not based primarily on such sources.

The Edmund pages on coatings look fine to me.--Srleffler (talk) 03:51, 25 March 2011 (UTC)

OK, the certificate is out. That was pretty much what I figured, but I wanted to be sure.

Other than being an occasional customer, I have no affiliation with Edmund, nor any other optics company. My interest in lasers is purely as a hobby. I was hoping to add a little back-up to some completely unsourced articles, but I'll see if I can locate some other sources to go along with it. I was a little nervous about this one. I've used primary sources before, like the Perkin Elmer Flash Catalogue or the US Naval Flight Instruction Manual, but this would be the first one that will actually sell to the general public. (By the way, I fully agree with your proposal to merge thin-film interference and thin-film optics, but have no clue about how to do that.)

Unfortunately for you, you've sort of become my go-to person here on lasers and optics. :-D So, on that note, I have one more question. I have no idea how to place math symbols in articles. I often write stuff like "1/20 wave," even though I know it's not correct. How do I put the upside-down "y" wavelength symbol into the photo's caption? Zaereth (talk) 06:06, 25 March 2011 (UTC)

The wavelength symbol is a lower-case greek letter lambda. There are three good ways to add it to an article. The easiest way is to use the character selector which is down below the edit box when you're editing a page (below the Save, Preview, and Show changes buttons.) Select "Greek" from the drop-down list, and click the character you want: λ. Another way to do it is to use html code: "λ" produces "λ".

The third option is to use Latex math markup: "<math>\lambda</math>" produces "${\displaystyle \lambda }$". Latex is a bit more cumbersome, and the font doesn't match the rest of the article. Where it shines, though, is that it allows nice typesetting of whole equations. It takes a bit of learning, but is not hard to use. You can learn more at Help:Displaying a formula.--Srleffler (talk) 22:40, 27 March 2011 (UTC)

Thanks! That'll help a lot! I'll keep trying to work up some improvements to some of these under-sourced articles. However, there is a limit to what I can glean from Google books. The local libraries often don't have what I'm looking for either, but I'll keep trying. (Most of what I know about thin-films came from studies of the tempering colors of steel.) Anyhow, thanks for your assistance, as you have been a great help. Zaereth (talk) 20:40, 30 March 2011 (UTC)

Thanks

Hello Srleffler,

thank you for your welcome! I am new to editing in WP and I appreciate your comments and hints. I think this is a beautiful place for sharing knowledge and learning, we all make it. Thanks again. ""Arconsoli (talk) 23:13, 8 April 2011 (UTC)

Thanks

Hello Srleffler,

thank you for helping me with the figures and articles. Jcc2011 (talk) 23:50, 30 April 2011 (UTC)

Luneburg Lens / Maxwell Fisheye

The attribution to C.A.S. was not irrelevant, as the original published version was not printed with any mention of Maxwell being the author (indeed it appeared instead as if the author was C.A.S.). — Preceding unsigned comment added by 155.198.198.134 (talk) 10:07, 1 July 2011 (UTC)

If there is a question about the authorship and you want to address it in the article, you should do so directly, not just by mentioning in passing whose initials appeared without explaining why this might be important. --Srleffler (talk) 05:28, 2 July 2011 (UTC)

A cup of coffee for you!

Curved mirrors

Thanks for your comments on my edits at Curved mirror! I am learning about the subject and was a bit confused by the books I'm using, so I wanted to make Misplaced Pages clearer for other interested learners out there. I wasn't entirely sure that my changes were correct (especially the minus sign I added to the equation, even though by my calculations that yields correct results) and was pleased to see an editor --who seems experienced on the subject-- validating the changes. I am curious though as to why some of these details are not clearly explained in many texts, especially the equation -- that confused me a bit until I figured out how to make sense of it. Specifically, I found it here on Misplaced Pages and in several web pages without the minus sign to the right side; Hecht's Optics states the right side as -2/R (fortunately, close to that they mention the convention that R>0 for convex mirrors and R<0 for concave ones, and since f=R/2, it made some sense), and on Falk's Seeing the Light, they derive it geometrically and end up at ${\displaystyle -{\frac {1}{d_{o}}}+-{\frac {1}{d_{i}}}={\frac {1}{f}}}$, but don't simplify it to the version I changed the article to. Do you think you could enlighten me a bit on why there are all these different versions around? Thanks, Waldir 14:16, 11 July 2011 (UTC)

I didn't notice that you had flipped the sign. I will check it out when I have a chance. I usually revert edits that flip signs in equations unless there is a good reason for the change, and a reference to a reliable source. As to why there are different versions of the equations in use, see Sign convention. It is very common in physics, and especially in optics, that one has to make an arbitrary choice when describing a physical system mathematically. Different choices change the signs of various terms in the resulting equations. The different forms of the equations all work, as long as you use the correct definitions when converting your physical quantities into mathematical ones. Failure to understand this is a frequent cause of errors in Misplaced Pages. Editors read an equation in a textbook, find that the signs don't match those in the WP article, and "fix" the equation in the article, without realizing that the article defines the quantities in a way that is incompatible with that form of the equation.

The choices in this case are whether f is positive for concave or for convex mirrors, and whether d_i is positive for real images, or positive for images that are to the right of the mirror (which are therefore virtual). Hecht's convention makes the sign of the focal length for converging mirrors the same as that for converging lenses, and in fact the mirror equation is then identical to the Gaussian lens formula. (In my 2nd edition copy of Hecht, these are equations 5.50 and 5.17, respectively). Note that in Hecht's convention f=–R/2, contrary to what you wrote above. I'm not familiar with Falk's book, so I can't check what his interpretation is. I will therefore likely switch the article back to Hecht's sign convention, but try to keep a clear explanation based on what you wrote.--Srleffler (talk) 17:10, 11 July 2011 (UTC)

Thanks. I do realize I misquoted Hecht, sorry about that. Anyway, I have no problem with the sign change being reverted (the previous version was neater anyway). As long as there is an explanatory text describing the choice of sign in the equation, there shouldn't be any confusion. Perhaps you can also mention that some texts use a different sign convention, so that people who learn the other convention don't get puzzled when they see a different equation. Btw, here's a link to David Falk et al.'s book: http://books.google.com/books?id=AvgsAQAAIAAJ. Cheers, Waldir 22:30, 11 July 2011 (UTC)

Your revision of 22 July http://en.wikipedia.org/search/?title=Boltzmann_constant&action=historysubmit&diff=440776071&oldid=435994660

I don't see your problem. Why do you write 'dubious' and ask for a ref.? The explanation seems clear to me, all it says is that the Boltzmann constant is applicable at the molecular level and higher levels (many molecules/particles) also. --Damorbel (talk) 09:54, 22 July 2011 (UTC)

It says that adding the Boltzmann constant "transforms the ideal gas law into an equation about the microscopic properties of molecules". Pressure and volume are not microscopic properties of molecules. They are bulk properties of a gas. Individual molecules have neither pressure nor volume.--Srleffler (talk) 17:06, 22 July 2011 (UTC)

"Optical vandalism"

(I avoid to use the person's user name in a readable form, so that he will not easily find this by a mere text search...)

A Hungarian guy from Rumania is producing lots of optical images, that look relatively nice (though old-fashioned), but are mostly inadequate for use in optics articles that want to explain things. So far, so good. But he forces his products down our throats, by replacing exisiting images in existing articles by his own ones. And even worse, he does so in all Misplaced Pages language versions, even in exotic lagnuages like Chinese, Japanese, Hebrew, Arab, and all others. He does not understand English (if he "communicates" at all, he does so via translation software). Recently, he even replaced an existing image on Commons by a totally different one form himself. Might this be his newest, much more "efficient" way to put his images everywhere (no more need to edit scores of foreign languages)?

Background info on the guy and his way of operation can be found here (in English).

One reason for hs actions seems to be that he does not like coloured images. He prefers photo-like drawings that look realistic (i.e. black and white, like most otical instruments until half a century ago). He does not (or does not want to?) understand that images in explaining articles must answer different criteria, such as educational value.

A few Germans and I are trying to have this guy blocked on at least the German Misplaced Pages. But the blocking procedure there is very formal and complicated. We need to have at least five people who support the request (and that us just the request, he is nit yet blocked then!).

If you happen to have a basic grasp of German, may I ask you to consider to help us in this? We would appreciate to see your signature here. As far as we can see now, the best time to sign here will be Sunday, 24th July, between 10:00 and 22:00 GMT (though these times are nit yet sure).

If you know of other people here at the English Misplaced Pages who might be willing to help, we would appreciate if you inform them.

Thanks in advance.

HHahn (Talk) 10:56, 23 July 2011 (UTC)

Thanks. I'll keep an eye out for his edits. I skimmed through some of your discussion page on him. His apparent habit of replacing images, especially on wikis where he doesn't speak the language, concerns me a lot. One has to be very careful when replacing diagrams (as opposed to photos), and certainly cannot do this without being able to check that the text in the article still applies correctly to the new image. Other of the habits you complain about bother me less.

I'm a bit concerned with the tone you take towards him in places. Misplaced Pages (at least English Misplaced Pages) values civility between editors. It is important to be civil and respectful, especially towards editors with whom you are having problems.

It is probably not a good idea to be canvassing editors who are not involved in the German Misplaced Pages, to vote on blocking a user there. Doing so will greatly weaken your case, and make dealing with real problems by this user more difficult.--Srleffler (talk) 19:50, 23 July 2011 (UTC)

For what it's worth, I just checked and his only edit to an article on my watchlist was replacing a poor-quality diagram with a much better one. I'm not fond of the style, but the diagram he replaced was really bad.--Srleffler (talk) 19:50, 23 July 2011 (UTC)

His edits on English Misplaced Pages this year mostly involve adding images, rather than replacing existing ones. Perhaps he has taken the complaints seriously and improved. I have much less of a problem with an editor who inserts images, even bad ones, than with one who replaces existing images with inferior ones. A bad image can always be removed or replaced later. It's harder to replace an image that was removed, if the change is not noticed quickly.--Srleffler (talk) 20:19, 23 July 2011 (UTC)

Thanks for the warning against canvassing people for voting on another WP> I wasn't aware indeed of the problems that might produce.

As for replacing images, he did so in Commons. That image was not widely used. But he may have tried the effect. When he later does this same on a larger scale, the problems become much greater that theu have been so far. After all, watch list only report edits in the article itself, not images that have been replced in Commons. So authors may not be aware that their articles are being ruined.

As for my tone: first orf all, my vocabulary in English is much more limited that in German (my native language is Dutch). I am especially lacking words needed to "intensify" the effect of statements. And please note that the whole process did not start recently. If I am not mistaken, it is something like a year ago that I started warning him. Also, he seems to "hide" himself behind his lack of English and the flaws of machine translation.

A German user has already hinted that a global vandalism block may be better, and simpler.

Anyway, thanks for your support!

HHahn (Talk) 12:48, 24 July 2011 (UTC)

Nomination of 31Knots for deletion

The article will be discussed at Misplaced Pages:Articles for deletion/31Knots until a consensus is reached, and anyone is welcome to contribute to the discussion. The nomination will explain the policies and guidelines which are of concern. The discussion focuses on good quality evidence, and our policies and guidelines.

Users may edit the article during the discussion, including to improve the article to address concerns raised in the discussion. However, do not remove the article-for-deletion template from the top of the article. Lagrange613 (talk) 17:43, 4 August 2011 (UTC)

Disambiguation pages

I acknowledge your note but must differ with you in certain cases. Oftentimes the content on the disambiguation pages is RANDOMLY ordered, with no discernible logical or order of importance. In such cases, Misplaced Pages appears to be unprofessional and sloppy! Such content should be ordered in some discernible, logical fashion, with a schema that is neither tacit nor random. Additionally, many pages contain items that violate Misplaced Pages Style Guidelines in various ways (e.g., they contain multiple links within a given item, or piped links that obscure the actual linked page). You'll note that the work I did improves rather than detracts from the "dab" pages I edited. Froid 10:44, 5 August 2011 (UTC)