Talk:Iridescence/Archive 1

Etymology

Iris is both Latin and Greek. From what I've seen, it seems that the sense of "rainbow", which lead to "iridescence" in English is Latin; I don't think the earlier Greek word quite had this meaning. So to me it makes more sense to say that iridescence is derived from Latin, although sure ultimately it's Greek. Not knowing either language or their histories with any authority, this is only what I glean from etymological dictionaries, but I think it's the best we can do right now. --Chinasaur 07:59, 18 July 2005 (UTC)

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Here's what the Oxford English Dictionary says:

[a. Gr. ιρισ, stem ιριδ-. The senses (except 3 and 6) correspond to those of the Gr. word; so also F. iris. The pl. irides is chiefly used in sense 4.]

Sense 1 given by OED says:

• "Gr. Myth. The goddess who acted as the messenger of the gods, and was held to display as her sign, or appear as, the rainbow; hence, allusively, a messenger."

Sense 2 says;

• "A rainbow; a many-coloured refraction of light from drops of water."

Sense 4 says:

• "Anat. A flat, circular, coloured membrane suspended vertically in the aqueous humour of the eye, and separating the anterior from the posterior chamber; in its centre is a circular opening, called the pupil, which may be enlarged or diminished so as to regulate the amount of light transmitted to the retina."

Sense 5 says:

• "Bot. A genus of plants, the type of the natural order Iridaceæ, natives of Europe, N. Africa, and the temperate regions of Asia and America; most of the species have tuberous (less commonly bulbous or fibrous) roots, sword-shaped equitant leaves, and showy flowers; formerly often called Fleur-de-lis or Flower-de-luce. Also, a plant of this genus."

Note that it explictly said "The senses, (except 3 and 6) correspond to those of the Gr. word." Michael Hardy 20:29, 18 July 2005 (UTC)

Now who can't read the dictionary?  ;) --Chinasaur 02:18, 21 July 2005 (UTC)

Phase

The article on Holography states that holograms do not record phase information, contrary to what this article on Iridescence claims. I'm not a specialist in this area of Physics, so I won't touch it. --AndreFillipe 17:36, 25 September 2006 (UTC)

I Thought the "dubious" refered to irridescence not being able to be photographed in a "normal" photo. After all there ara two photos of irridescent colours accompanying the article :-)Ddcorp2000 08:44, 5 May 2007 (UTC)

Holography does record phase information (see for instance Eugene Hecht's book on optics). Iridescence cannot be photographed in the "normal" way in the sense that the picture will not change if you change its orientation. The original object's colours would depend on angle of observation.

There is a very long argument in the holography talk page about whether or whether not is is accurate to say holograms stores phase information. It appears to be more a matter of semantics then an actual dispute of the physics and from what I can tell the 'does store phase information side' won. Also, as anon above said, irridescence can't be photographed in the sense the photographed image does not display irridescence. So I've removed the dubious tag Nil Einne 10:37, 21 July 2007 (UTC)

Merger proposal

I posted the templates proposing the merge. Cloud iridescence is an example of iridescence and should be a section in the iridescence article. The cloud iridescence article should then be redirected to the apropriate section of the iridescence article. If someone agrees, feel free to merge the pages. If someone disagrees, discuss here. If no one cares, I'll merge them in a couple weeks when I find the time.Garvin ^Talk 16:42, 18 April 2008 (UTC)

I agree. Cloud iridescence is not notable by itself and will do much better in the Iridescence page. IceUnshattered (talk) 23:07, 8 May 2008 (UTC)

The article does have encyclopedic value beyond iridescence alone. A merger would likely entail implementations in both cloud and iridescence.   — C M B J   03:38, 1 August 2008 (UTC)

I oppose the merger. Cloud iridescence is notable in its own right. Iridescence is normally associated with surfaces of solid object surfaces or fluids, not gasses or vapors, and the physics would be different. --George100 (talk) 07:44, 12 August 2008 (UTC)

If the merger failed, would you be willing to provide reliable references and do cleanup on the article? Is there any reference you can find that states that iridescence is usually associated with solids or fluids? IceUnshattered ^{[ t ]} 17:17, 6 September 2008 (UTC)

Something wrong here. Irisation (a page I just put up) "are formed from small water droplets of near uniform size" (have a look at [1] and [2]). According to the Answers.com reference at the bottom of the Cloud iridescence page[3], that phenomenon is caused by "ice-crystal(s)" (although I have learned not to trust Answers.com on these things). Fountains of Bryn Mawr (talk) 00:40, 3 November 2008 (UTC)

Oppose merger. There are many sources of cloud color and iridescence is a specific mechanism. It is a sky optical phenomenon and deserves to be treated separately as such. --Halos25 (talk) 12:17, 18 July 2009 (UTC)—Preceding unsigned comment added by Halos25 (talk • contribs) 12:13, 18 July 2009 (UTC)

Iridescent?

The tapetum lucidum is often described as iridescent, but it is principally a retroreflector; would iridescence indicate sub-optimal retroreflection? Or, is the iridescence due not to the tapetum lucidum but to the choroid in which the tapetum lucidum is embedded? --Una Smith (talk) 04:17, 3 June 2008 (UTC)

I would say that the membrane itself may be iridescent. I'm trying to remember it in a dissection I preformed. The test would be to whether the color changed with viewing angle. The picture on the article page suggests this is the case. However, the "eyeshine" effect observed in a live animal having a tapetum lucidum is not notable for iridescence. Also, from an evolutionary standpoint, I would not be surprised if iridescence is the reason that there is no blur from the tapetum lucidum: photoreceptors are maximally sensitive to particular wavelengths, so at low light (nocturnal) conditions, only certain wavelength / reflective angle combinations would be striking the photoreceptors. I'll end my reply there because I am crossing into heavy speculation and not researched knowledge.Garvin ^Talk 15:40, 22 June 2008 (UTC)

Thanks for that. Since asking my question above I researched the literature some more. Descriptions of the tapetum lucidum as irridescent indeed are from dissections. In those, the shape is deformed. In situ, the TL is seen through the lens and there is no apparent irridescence. One very old study makes this distinction. --Una Smith (talk) 19:19, 22 June 2008 (UTC)

Disambiguation of pearlescent, iridescent, opalescent

pearlescent=finely divided reflective white or grey (as of a pearl)
iridescent=finely divided reflective monochromic (one color, like a pupillary iris)
opalescent=finely divided reflective polychromic (many colors, like an opal)
These words are often used interchangeably, but do offer a distinction. That distinction provides a means to explore perhaps three different categories of structure and effect: pan/achromatic, monochromatic and polychromatic.
The lovely but complex effects which are implied under these three words (and some others) are based on similar effects, but multiple processes in a wide variety of materials. I believe all reflect the effects on light of structure rather than pigments.
That said, many such materials also include pigments which can add or detract from the visual effect, but the effects of pigments should be considered separately. To complicate this effort, it is possible to produce an approximation of some of these effects with finely divided domains of pigment in a clear medium.
The structure of certain natural and artificial materials affects incident and reflected light based on the dimensions and orientation of those structures. Therefor, the angle of incidence, and angle(s) of observation (with respect to the material orientation) can strongly affect the effect. Therefor, when compared to a photo, the effect is enhanced by stereoscopic (observing 2 angles at once, causing apparent scintillation because of the difference perceived by each eye) and dynamic observation (moving source, object, or eye, provides a sequence of angles, causing true scintillation (visible changes with time)).
{More later?}
Wikidity (talk) 01:26, 4 April 2010 (UTC)

File:Tachinidae.jpg to appear as POTD soon

Hello! This is a note to let the editors of this article know that File:Tachinidae.jpg will be appearing as picture of the day on July 28, 2010. You can view and edit the POTD blurb at Template:POTD/2010-07-28. If this article needs any attention or maintenance, it would be preferable if that could be done before its appearance on the Main Page so Wikipedia doesn't look bad. :) Thanks! howcheng {chat} 18:56, 26 July 2010 (UTC)

Picture of the day

A tachinid fly (species undetermined), where the iridescence on the wings is visible. Iridescence is an optical phenomenon where the colour of an object changes as the angle of view changes. It is caused by multiple reflections from multi-layered, semi-transparent surfaces in which phase shift and interference of the reflections modulates the incident light.Photo: Muhammad Mahdi Karim