User talk:Srleffler

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Hi, feel free to leave me a message. Kindly leave messages on new topics at the bottom of this page. Srleffler

Disambiguation pages

User talk:Froid

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, Wikipedia 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 Wikipedia 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)

Saw your most recent messages and wanted to reply. Thank you for the feedback, which I take to heart and will adhere to. I made the changes in good faith but did not mean to cause damage or create additional work for other editors. Please accept my apologies. Best wishes. Froid 14:22, 7 August 2011 (UTC)

Thanks for reconsidering. You're doing good work cleaning up dab pages. There are certainly lots of them that do need attention, and relatively few editors who enjoy cleaning them up.--Srleffler (talk) 15:30, 7 August 2011 (UTC)

Italicization of subscripts

You have a point. I'm not sure how universal such a convention is—I've never noticed it before—but it seems intuitively plausible. However, as it stands now Fresnel equations is inconsistent in its italicization; the i, r, and t subscripts in the figure and the rendered TeX are still italicized. I find this distracting, which prompted my (perhaps ill-considered) edit(s). I could change the TeX, but replacing the figure is more work than I care to do, unfortunately. Also, the s and p subscripts should be italicised, so I guess I'll revert that subset of your reversion. But thanks for bringing this to my attention. False vacuum (talk) 03:09, 8 August 2011 (UTC)

Quite confident now that you and the Manual of Style are correct about this, and can't believe I made that mistake. False vacuum (talk) 04:36, 8 August 2011 (UTC)

Update: Fixed the TeX. (One formula had two ts in it that meant different things! Would have noticed—and probably not made the original mistake—if I'd actually read the article.) False vacuum (talk) 05:15, 8 August 2011 (UTC)

I'm not sure why you think the s and p subscripts should be italicized. They have the same nature as i, r, and t. The s and p are the first letters of the German words for parallel and perpendicular. They are purely descriptive labels, not variables that can take on different values.--Srleffler (talk) 04:27, 9 August 2011 (UTC)

I thought that because I still wasn't really paying attention, I guess. Sorry. (I was going to fix it, just now, if someone hadn't already.) False vacuum (talk) 09:51, 10 August 2011 (UTC)

See also, Ruby Laser

Hello, you reverted my edit. Maybe you were right to do that, but is it good practice to have an empty "see also" section? Larryisgood (talk) 12:41, 25 August 2011 (UTC)

The section wasn't empty. There was a Wikimedia commons link at the right hand side. --Srleffler (talk) 01:03, 26 August 2011 (UTC)

Sorry for the oopsie on the laser page

I'm too much of a AWB newbie to be using a script, I was confused because there was a newline where the caption started; in the future I will take more pains to preview any changes I make. Thanks for pointing that out to me. Alanl (talk) 01:26, 29 August 2011 (UTC)

Radiance Article

"The last edit presumes radiance is conserved, which is not always true."

I see your point. However, I am trying to rationalize the definition, which says L is the observed or measured radiance and $\frac{\mathrm{d}^2 \Phi}{\mathrm{d}A\,\mathrm{d}{\Omega}}$ is the radiant flux per steradian. It appears that the definition is an implicit correspondence between an emitted radiance and a measured radiance. Therefore, anytime the definition is applied there is an implicit emission surface and detector surface. Granted, these surfaces may be infinitely close so that there is no opportunity for scattering and other losses. I understand that the way I originally wrote it implies something that is not always correct. However, I wanted to clarify why L and $\frac{\mathrm{d}^2 \Phi}{\mathrm{d}A\,\mathrm{d}{\Omega}}$ have the same units but differ by a 1 over cosine term. The answer is that they are talking about solid angles defined from different perspectives and areas of different surface. Any advice on how to rectify this confusion in a rigorous sense. — Preceding unsigned comment added by 205.201.252.91 (talk) 18:58, 22 September 2011 (UTC)

The cosine term is a geometric factor. The area of the source element as seen from the detector is dA cos θ. The emitting angle looks smaller if you're looking at it from a steeper angle relative to the surface normal. If this isn't clear, imagine a source that is a flat square plane of area A. If you look at it almost edge-on (say 89° to the normal), the plane appears very narrow. The visible area is A cos θ.

While the definition in the article is written in terms of a source and detector surface, I do not believe this is necessary (it is a flaw in the article). One can define the radiance at any plane or curved surface in the beam, based on the spatial and angular distribution of the light. This is related to etendue. I don't understand the topic well enough to elaborate on this point, or to fix the definition in the article.--Srleffler (talk) 05:33, 24 September 2011 (UTC)

Riboflavin

http://en.wikipedia.org/wiki/Talk:Riboflavin#outside_from_text --Palapa (talk) 23:12, 22 September 2011 (UTC)

Page moves

Hi,

When making edits like this, please take the time to ensure that the talk page archives and any associated automatic archiving are corrected to match the new title. I've now done this for you, even though I'd suggest that WP:ACRONYMTITLE favours using unambiguous industry-standard acronyms like OLED anyway. Chris Cunningham (user:thumperward) - talk 09:21, 4 October 2011 (UTC)

Sorry for the incomplete page move. I didn't think to check for that.

My reading of WP:ACRONYMTITLE, is that being "industry-standard" is not sufficient. To use an acronym as a page title, the subject must be "exclusively known by its acronym or ... widely known and used in that form". The Manual of Style recommends checking popular publications such as newspapers, magazines, etc. to determine whether this is the case. So, the question is, whether a newspaper article could refer to an "OLED" without spelling out what the acronym stands for. I highly doubt that the acronym is sufficiently well known for that. On the other hand, the examples given in the guidelines, such as NATO, NASA, laser, and radar, are so much better known by their acronyms that some readers might not recognize the name if written out in full.

Besides the guidelines, there was a discussion of this topic on the talk page, with the consensus reached being for the current article title. That precludes moving the article to the rejected title without a discussion to establish a new consensus.--Srleffler (talk) 01:51, 5 October 2011 (UTC)

With the exception of the journals (which are obviously going to spell out acronyms) I see pretty universal use of "OLED" over "Organic light-emitting diode" in the current sources. Bxj pointed that out in the linked discussion, which was a terribly weak head-count close. The idea that any acronym less universally used than "laser" has to be spelled out certainly isn't congruent with established practice. If I have to request another page move (for both this and AMOLED) then so be it. Chris Cunningham (user:thumperward) - talk 10:02, 6 October 2011 (UTC)

I see your point. A quick search finds much broader use of "OLED" as such than I had expected. It appears that with growing use in displays it has become a much more common acronym than I had realized. My opinion on the required standard has not changed, but perhaps "OLED" meets it. I don't think the article should be moved without a new talk page move discussion, but I might not oppose the change in such a discussion.--Srleffler (talk) 23:39, 6 October 2011 (UTC)

Planck's Law

There is a question as to the best notation for spectral radiance in the Planck's law article in terms of wavelength and frequency. Presently I(ν,T) and I'(λ,T) are being used for the frequency and wavelength functions, but the idea is that I_ν(T) and I_λ(T) would be more informative, while remaining in the mainstream of present usage. Any opinions would be welcome. PAR (talk) 04:22, 11 October 2011 (UTC)

Another problem in Planck's law - to convert from spectral radiance in frequency units (I_ν), to some other variable x (e.g. wavelength) we must use | I_νdν | = | I_xdx | where x is a monotonic function of frequency ν. Do you happen to know of a reference for this general statement? Thanks for any help. PAR (talk) 03:45, 1 November 2011 (UTC)

Not offhand, no.--Srleffler (talk) 03:48, 1 November 2011 (UTC)

Hello again - we are having some serious terminology problems on the Planck's law discussion page. We need to make our terminology consistent with other Wikipedia articles, and I know that you have given this subject some thought. I will try to boil it down.

First there is something called $I_\nu(\mathbf{n})$. This has units of power/area/solid angle/frequency so that $I_\nu(\mathbf{n})dAd\Omega d\nu$ is the power radiated into a small solid angle dΩ about the normal to a small imaginary area element dA whose normal points in direction $\mathbf{n}$ in a small frequency band dν. Isotropic radiation means I_ν is independent of direction $\mathbf{n}$ where $\mathbf{n}$ can point in any direction whatsoever. There are no physical surfaces involved or considered.

Next is the consideration of a real physical surface. The $I_\nu(\mathbf{n})$ coming out of a physical surface is, lets say, $R_\nu(\mathbf{n})$. It refers only to the radiation leaving a surface, not to that entering. If you take the imaginary area element mentioned above, immersed in a radiation field $I_\nu(\mathbf{n})$, and pick a side of that area element, then consider only the radiation passing out of that side, that radiation could correspond to the $R_\nu(\mathbf{n})$ of a real physical surface at that point and in that orientation. If the $I_\nu(\mathbf{n})$ were isotropic, then I have been saying that the corresponding $R_\nu(\mathbf{n})$ is isotropic. However, if a surface is characterized by isotropic $R_\nu(\mathbf{n})$, that does not mean the $I_\nu(\mathbf{n})$ is isotropic, because the radiation into the surface may not match the radiation leaving. Any thoughts you have on the Wikipedia-standardized terms for these quantities and concepts would be very welcome.

Finally there is the question of Lambert's cosine law article which states that the radiance from a Lambertian surface is proportional to the cosine of the angle from the normal, which, if radiance is $R_\nu(\mathbf{n})$, is wrong, it should be constant. In the definition of radiance from the radiance article, it is clearly including the cosine in the denominator, meaning that the "per unit area" in the definition of radiance is "per unit of projected emitting area", not "per unit of the emitting area", which would mean that isotropic radiance is constant with respect to direction. Also, regarding a real physical surface, what would be the term corresponding to power/area/solid angle/frequency out of the surface where the area element is the emitting area, not the projection of the emitting area?. This quantity would show cosine dependence with angle. Again, any thoughts you have on the Wikipedia-standardized terms for these concepts would be very welcome. PAR (talk) 00:15, 17 November 2011 (UTC)

Lens (optics)

Dear Srleffler

Not was was a good step that you removed my pictures. I tried to give as many infornations related to the lens. With your intervention page looks pretty weak now. Instead of making unnecessary changes, which spoil the appearance, please make a major change to the section "Compound lenses - Link: [[1]](i read that you are a specialist in optics)" explains the practical calculations and drawing a combination of two lenses. The choice is yours - thin or thick lenses. It would be very useful for readers. Or if you disturbing examples of calculation on the page. Make a new section designation of "Practical optical calculations." It would be something. Where could you explain how to calculate the different systems and combinations of lenses (at a level understandable to readers - not complicated,simple and practical!). It would be a page that you use as a reference for basic page. Regards, --Tamasflex (talk) 07:12, 5 November 2011 (UTC)

Ps: Not every reader is familiar with the equations. It is easier to write equation, but it's hard to explain in such a way as to be understood by readers who are not familiar in optics. Few examples of calculation does not spoil the look.

Equations need to be in HTML or Latex markup, not in an image file. This allows them to be edited by other editors. Also, a block of equations with no explanation is useless and inappropriate. If you want to write a section on the thick lens equations using proper English prose and editable equations, do that. Don't just stick an image file full of math into an article.--Srleffler (talk) 21:20, 5 November 2011 (UTC)

Merge interference (optics) and interference (wave propagation) articles

I have drafted a merged article at user:epzcaw/Interference (wave propagation). Comments welcome. Epzcaw (talk) 14:04, 8 November 2011 (UTC)

Friction

Hello. I appreciate your answer at Friction, but some of the explanation is still unclear. I wasn't sure whether typos has crept in.

"Each grain of sand exerts a force F_f = μF_N from the moment it hits the belt until the grain reaches the belt's speed vb. After the grain gets up to speed, it no longer exerts a force on the belt. A little math will show that the time required to get up to speed is $t_b={v_b m_g \over F_f}={v_b \over \mu g}$, where mg is the mass of the grain and g is the gravitational acceleration."

For example, what is F_N? μ is grain mass, I presume. I can see that $t_b={v_b m_g \over F_f}$, but not why it equals ${v_b \over \mu g}$, and why is gravitation is relevant? (I imagine an alternative set up where it is a spaceship traveling through zero g at a steady 0.1m/s while 'sweeping up' space dust in a bucket on the nose cone at a rate of 2kg/s.)

In short: could you make it all very explicit? Thank you. Ammimajus (talk)

No, F_N is the normal force and μ is the coefficient of friction. This notation is used in the article, so I didn't bother to explain it. See Friction#Dry friction if you need a reminder of how dry friction works. The grain mass is m_g as I stated explicitly, and as you quoted me above. Gravity comes into the problem because the normal force is the weight of the grain of sand F_N = m_gg.--Srleffler (talk) 05:55, 19 November 2011 (UTC)

Thank you very much! That is very helpful. I get the calculation and am happy with it. The textbook says about the conveyor belt: "the extra power is twice the kinetic energy imparted to the sand because the sand does not immediately assume the velocity of the belt so that the belt moves relative to the sand. The extra power is needed to overcome the friction between the sand and belt." Perhaps the last sentence is worrying me too. It is not such much that it has to "overcome friction" but rather "work with the friction" to produce the force to accelerate the sand grains. What is surprising is that there seems to be no half way house between "immediately assuming" the speed of the belt and very gradual (asymptotic even) acceleration. Suppose we started with a certain amount of sand lying on a stationary belt and the belt accelerating to a certain velocity? Would the "wasted energy" (total energy required minus final total kinetic energy) be the same (50%)? And what about the alternative of the space rocket collecting sand in a bucket. The sand hits the bottom of the bucket...the rocket must expend some energy to keep going at the same speed with extra mass. Is that case different and why? Ammimajus (talk)

Yes, the book's comment about "overcoming the friction" is strange and misleading. It is the friction that allows the belt to impart horizontal motion to the sand.

Friction is kind of an odd force, because it changes depending on whether the two objects are moving relative to one another. If one object is sliding against another, the friction force is determined by the coefficient of kinetic friction. If the object is not sliding, one instead gets static friction, which is much stronger. In practice, this means that if a sliding object's relative velocity drops below a certain value (which probably depends on the materials and their surface structure), the surfaces will "grab" and bring the moving object to a halt relative to the other object.

If you start with sand lying on the belt and the belt stationary, as long as the force the belt exerts on the sand is less than the static friction force, the sand will accelerate with the belt. If the belt accelerates too fast, the force it exerts on the sand will exceed the static friction force and then the sand won't keep up with the belt's acceleration. Energy will be wasted due to the sand sliding on the belt.

The case of the rocket collecting sand in a bucket is different because there is no friction. Assuming the sand goes into the bucket and sticks, the energy the rocket has to expend should equal the kinetic energy imparted to the sand.

As I noted in my comments on the talk page, the fact that the belt accelerating the falling sand has to expend more energy than the kinetic energy imparted to the sand should not be surprising. The sand is sliding against the belt, which generates heat through friction. That energy has to come from somewhere, and in fact it comes from the belt.--Srleffler (talk) 04:57, 20 November 2011 (UTC)

Merry Christmas!

Hi Srleffler, long time no see. I just wanted to stop by and wish you a Merry Christmas. Your knowledge, wisdom, and willingness to help has always been an inspiration for me. I hope the coming New Year will bring you much happiness. Zaereth (talk) 08:26, 24 December 2011 (UTC)

Thanks

Thanks for your last night's Sharplan editions! Etan J. Tal 09:15, 30 December 2011 (UTC) 09:15, 30 December 2011 (UTC)

Edits on List of plasma (physics) articles

Thanks for editing List of plasma (physics) articles yeah it did have some red link errors in them. Some links like spacequake had the red links plasma vortices and Plasma jets in it, but I guess it makes more sense to change it. What do you think about me possibly making a list of laser articles that would probably be close to a 1000 links in it. I already made one on word pad. I figured it might help find laser links that need more info in it and more be more known. List of applications for lasers is decent but a list of laser articles will be more universal. Love the airborne laser. Maybe this time not in alphabetical order of the phoenix kind.Shawn Worthington Laser Plasma (talk) 20:23, 3 January 2012 (UTC)

I think a list of laser articles is just as pointless as a list of plasma articles. :) --Srleffler (talk) 05:15, 4 January 2012 (UTC)

SI chart in Luminos energy

Please go here: International System of Units — Preceding unsigned comment added by Algamicagrat (talk • contribs) 17:12, 7 January 2012 (UTC)

I'm familiar with the SI system. What is your point?--Srleffler (talk) 21:07, 7 January 2012 (UTC)

What I am pointing out is that really how can the Luminous Energy be part of the metric system. I mean yes it can be a unit of measure in the metric system but actually the page has really nothing about the Luminous Energy units. My point is that maybe I should not have put an electromagnetic spectrum picture/section but I googled Luminous Energy Units and got this page http://www.mediacollege.com/lighting/measurement/ and I got those units of measure. In my opinion the table on the page is not accurate. Me!!! Algamicagrat 01:10, 8 January 2012 (UTC)

I see. Take a look at SI derived unit. Lumen seconds are listed there, under "Examples of derived quantities and units". The page google found you is not very good. It's poorly written, far from complete, and the definition of the candela that it gives is 33 years out of date. (The definition was changed in 1979.)

I notice that you copied the material on that page in your first attempt at improving the article. Don't copy material from external websites into Wikipedia. We take copyrights very seriously, and cannot accept material copied from external sources unless we are licensed to use it.--Srleffler (talk) 04:54, 8 January 2012 (UTC)

Dude I did not. I mean maybe I kept a few sentences but it is paraphrased. I am sure maybe you didn't notice that I did rewrite sentences.Me!!! Algamicagrat 21:57, 8 January 2012 (UTC)

I saw that you tried to paraphrase, and that's great. At a glance the text looked too close to the original. I didn't do a detailed comparison of the two. I just wanted to make sure you know that you can't copy stuff in from other sites. Just changing a few words here and there isn't enough; the material has to be really rewritten.--Srleffler (talk) 05:07, 9 January 2012 (UTC)

Well I understand. Thanks for the feed back. Me!!! Algamicagrat 22:31, 9 January 2012 (UTC) — Preceding unsigned comment added by Algamicagrat (talk • contribs)

Re: Cybercopyedit, Optics, Alhazen, etc.

Thanks for the cleanup... the main complaint i had with the additions was that it was a all puffery that imparted or summarize no verifiable information (in fact it did not even summarize, and constituted a content fork with, the main article: History of optics... not that both could be pretty wrong) I will probably add some more content along these lines.

I would note that this user did not respond to your complaint or "comply with policy" "by creating a new (user name)". He/she is simply switching back in forth between pre-created user names as suits his/her purpose[2][3]. Sock puppetry/meat puppetry has been a hallmark of these Alhazen POV-PUSHes before but not this open or "ham fisted" right off the bat..... so I am will to assume a little good faith in that this may be a whole new inexperienced editor spouting the same line that large scale reference to Alhazen et-al is "vital" and "fully referenced" (echoing "the great minds of these men should be recognized at all costs"[4]). Fountains of Bryn Mawr (talk) 15:16, 12 January 2012 (UTC)