Talk:Total internal reflection

message: Perhaps a brief description of dispersion would be appropriate.
:Done? The "History" section now notes that Newton "pointed out the relationship between TIR and dispersion..." — Gavin R Putland (talk) 12:34, 3 May 2019 (UTC)
thread_title:  Dispersion 

message: Light is shown propapagating along the interface when incident at exactly the critical angle.  But doesn't this violate the principle of reversibility?  Instead, shouldn't the light should be reflected if incident at exactly the critical angle?
-- cheers, Michael C. Price talk 07:21, 20 January 2013 (UTC)
replies: text: (I hope), by adding a footnote to the caption and (earlier) by generally referring to the tangential ray as a limiting case. — Gavin R Putland (talk) 06:36, 7 May 2019 (UTC)
thread_title: At the critical angle

message: I'm working on a major revision of this article with some requested features, including more citations, details on the phase shift, and the effect of absorption of the evanescent wave. The target date is 31 March 2019 (after which I'll be out of action for a while). — Gavin R Putland (talk) 12:46, 21 March 2019 (UTC)
replies: text: — Gavin R Putland (talk) 12:52, 12 April 2019 (UTC)
thread_title:  Major revision 

message: I intend to add a "History" section in the near future. — Gavin R Putland (talk) 14:32, 12 April 2019 (UTC)
replies: text: — Gavin R Putland (talk) 13:56, 22 April 2019 (UTC)
thread_title:  "History" section 

message: I submit that the article Total internal reflection, of which I admit being main author, meets all the criteria for an A-Class article (WP:ACLASS), together with selected criteria for a featured article (WP:FACR), as follows. (P.S.: And for any interested WikiProjects that do not recognize A-Class articles, I hope the following points make it easy to upgrade this one to B Class! — Gavin R Putland (talk) 04:14, 4 June 2019 (UTC)
thread_title:  Submission on promotion to A-Class 

message: The file: https://en.wikipedia.org/wiki/File:Wavefront_refraction_slow_to_fast.svg 
As far as I can tell the image inverts the actual refractive speed/angle relationship. Presumably this is due to the accidental swapping of (the rays' angles with the line-normal-to-the-media-interface) for (their angles with the interface itself).
Let me know if you think I'm simply the one who's confused here, but I've spent a good bit of time confirming to myself that indeed the angle of transit should become more nearly perpendicular to the interface when going from a faster (/lower index of refraction) to a slower (/higher index) medium, in accord with the principle of least time  etc.
I can't just reidentify "medium 1" as that with the higher speed in the file description and article text (and substitute cosine for sine), given the speed-magnitudes depicted alongside each ray.
I can/will try to eventually edit and replace the image but given my minimal image-editing experience, superseding priorities, and that I'm just now downloading Inkscape for the task, the result will probably be days or weeks forthcoming and somewhat stylistically inconsistent with the article's other graphics. Until then I hesitate to act unilaterally e.g. by delinking the image, just in case I'm somehow still beset with a misconception here.
While the risk of confusing newcomers to the topic is perhaps lowish because the overwhelming bulk of the article including its other images are accurate, it still makes me fret.
Nonetheless many thanks to User:Gavin_R_Putland for the extensive expository work!
Riyuky (talk) 14:29, 22 January 2021 (UTC)
replies: text: Riyuky: The red line shows the wavefront, not the ray. The angle between the interface and the wavefront (θ1 or θ2) is the angle between the normal to the interface and the normal to the wavefront. In the special case of an isotropic medium, the latter normal is in the ray direction, so that the angle between the normals is the "angle of incidence" or "angle of refraction"; and if, as here, the wavefront is refracted towards the normal to the interface, the ray is refracted away from it. Medium 1 has the lower speed, and the direction of incidence is from medium 1 to medium 2, i.e. from bottom to top, for consistency with the oft-mentioned example of internal reflection from a water-air surface. I have amended the caption in an attempt to make some of this clearer. — Gavin R Putland (talk) 01:06, 23 January 2021 (UTC)
replies: text: Thanks for the clarification! The image does of course make sense in this light. I now realize I had idiosyncratically interpreted the arrows as depicting the relative speeds of constituent spherical wavelets' propagation orthogonal to the plane-waves' directions of travel (as in https://en.wikipedia.org/wiki/File:Refraction_-_Huygens-Fresnel_principle.svg ) to conveniently illustrate those speeds, even though there aren't resulting orthogonal plane-waves. Riyuky (talk) 01:59, 12 February 2021 (UTC)
thread_title: Apparent error in "Figure 4" as of this edit

message: Hello! This is to let editors know that the featured picture :File:Internal reflection, Anna.jpg, which is used in this article, has been selected as the English Wikipedia's picture of the day (POTD) for September 13, 2021. A preview of the POTD is displayed below and can be edited at Template:POTD/2021-09-13. For the greater benefit of readers, any potential improvements or maintenance that could benefit the quality of this article should be done before its scheduled appearance on the Main Page.  If you have any concerns, please place a message at Wikipedia talk:Picture of the day. Thank you! Cwmhiraeth (talk) 12:25, 28 August 2021 (UTC)
thread_title:  Featured picture scheduled for POTD