Talk:Mirage
From Wikipedia, the free encyclopedia
Contents |
[edit] Highway Mirage
While closely related, and they certainly should be linked, I see two seperate articles on Mirage and Highway mirage as making sense. I grew up seeing a lot of highway mirages in the Oregon desert. dino 20:07, 19 April 2006 (UTC)
- They're the same phenomenon! Sometimes I just can't understand why people want to keep articles separate (note spelling). —Keenan Pepper 21:24, 19 April 2006 (UTC)
-
- Yes, there is absolutely no reason to have a separate article on "highway mirages". It is exactly the same phenomenon as a desert mirage. The only difference is that it happens to occur on a highway. --Srleffler 12:03, 26 May 2006 (UTC)
I moved the material Dino added from the former highway mirage article to a subsection of "inferior mirage", where it belongs. The material is completely redundant with what is already here, but it does explain the phenomenon in a nice, simple way. The redundancy is still annoying, though. Maybe later I'll look at incorporating the nice simple explanation into the main "explanation" section.
BTW Dino: '#' section references don't work on redirects.--Srleffler 21:39, 30 May 2006 (UTC)
[edit] obnoxious mathematics
Srleffler, you changed the normal adiabatic gradient from +1 to -1°/100m. Although more correct, now the statement: smaller than -1° is confusing. Mathematically speaking -1.1 is a valid solution, but intuitively speaking people will think of -0.9 etc. (In fact the latter is meant). Please think about some rewording.
Likewise ±3 is mathematically speaking +3 or -3 (as the solution of the square root of 9). ~3 for 'circa 3' would be better, as was intended. But maybe less known. Some rewording?
Oh, and thanks for general cleaning up my English --Tauʻolunga 20:02, 26 May 2006 (UTC)
I agree with you about "smaller than". I was hoping this would be less confusing than "less than" (since smaller might imply magnitude rather than value), but apparently this doesn't work. I changed it to "about -1". If you have a more precise value, substitute it in.
Where I wrote ±2, I really meant +2 or -2, not "circa 2". Clearly it is the magnitude of the gradient that matters, so either +2 or -2 is sufficient to produce a mirage.--Srleffler 22:12, 26 May 2006 (UTC)
- I see. However the values quoted were for an inferior (-) image only. Values for the superior (+) image were not given. But I reckon that we can keep it like this until someone comes with additional data. --Tauʻolunga 00:56, 31 May 2006 (UTC)
[edit] Word Origin
Mirage is called "Mareechika" in Sanskrit (Ancient Indian) language. Can someone tell me whether there is any relationship between these two? If thats true, it might have originated from Indo-Aryan word rather than from something like 'Mirror' !—The preceding unsigned comment was added by Shreeshiri (talk • contribs) .
- The SOED and Chamber's Dictionary of Etymology agree that it comes from the French mirage, from mirer "look at", from the Latin mirare "wonder at". It's related to the Sanskrit smayas "surprise, astonishment", but not to mareechika as far as I know. —Keenan Pepper 23:21, 16 June 2006 (UTC)
[edit] Total Internal Reflection
Here's a bit of "original research." I've always had niggling doubts about mirage explanations. Mirages to me appear suspiciously similar to Total internal reflection. At just this moment my doubts solidified: as light moves from a dense medium to a less-dense medium, light is refracted as its angle changes proportially to the difference in refractive indices... but the angle never becomes negative. Refractive transitions between media can only bend light, not reflect it. However, if light leaves a dense material and enters a rarified material at a glancing angle, and this angle is less than the Critical angle of total internal reflection, the light will be 100% reflected. Therefore, since refraction only causes bending, while TIR causes reflection, hot-road mirages are an example of internal reflection. But I've never seen this explanation anywhere. I suspect that the standard refractive-bending explanation of mirages may be a galloping myth, an "infectious textbook misconception." How could we decide this issue? Easy: if light glances off the heated roadway at more than the Critical angle, the light will split into two paths: a weak reflection and a strong refraction. As the incident angle decreases, suddenly the reflection goes to 100% and the refraction goes to zero. If such a thing occurs with roadway mirages, then those mirages are caused by internal reflection phenomena and not by simple bending of light as is usually explained. I found a reference which points out that if mirages were refractive, they would be rainbow-colored because of dispersion. Since such dispersion is not seen, and mirages appear to be 100% mirrors, they are internal reflections and not refractive bends. --Wjbeaty 06:58, 30 October 2006 (UTC)
- That does make sense, intuitively. I found several pages which seem to support the idea of mirage as TIR, for instance: [1], [2], and [3]. It's been way too many years since my last optics class -- so I'll refrain from actually attempting to introduce this concept into the article. --Dfred 21:19, 24 February 2007 (UTC)
