Goal twoaie
[[Coadan:Double-alaskan-rainbow.jpg|thumb|right|300px|Goal twoaie dooblit lieh-chiarkylagh. Ta tooilley goalyn twoaie er çheu mooie ny h-ard-chruillag.]]

She phenomenon [[reayrt-oaylleeaght|shilleydagh]] as [[emshyraght|emshyragh]] eh '''goal twoaie''' ('''goll twoaie''', '''Bhow Ghorree'''). T'eh cur er [[spectrum reayrtagh|spectrum sollys]] çheet rish 'sy speyr tra ta soilshey ny greiney bentyn rish bineenyn ushtey 'syn [[aeraght ny cruinney|aeraght]]. Ta cummey [[cruillag]] yl-daahagh echey, as jiarg er y çheu mooie echey, as gorrym-jiarg er y çheu sthie. She spectrum gyn creeaghyn t'ayn, agh ta sleih cliaghtey rheynn eh ayns daahghyn discreajagh. Hug [[Isaac Newton]] queig daahghyn da: jiarg, buigh, geayney, gorrym as "''violet''" (cummey gorrym-jiarg gyn fockle 'sy Ghaelg, myr daah [[lus y chree]]). Hug eh stiagh jiarg-bwee as plooreen ny s'anmey rere [[aarey chiaull]].<ref>{{enmyseddyrvoggyl
  | kiangley = http://www1.umn.edu/ships/updates/newton1.htm 
  | screeudeyr = Douglas Allchin
  | ennym = SHiPS Resource Center for Sociology, History and Philosophy in Science Teaching
  | obbyr = Newton's Colors
  | datefeddyn = 2010-08-03
  | çhengey = Baarle
}}</ref>  Cha nel dagh çhengey cur ny daahghyn cheddin da.

Cha nee fliaghey ynrican nod ve ny vun goal twoaie; t'ad ry-akin ayns [[kay]] as spreie myrgeddin.

[[Coadan:TakakkawFalls2 edit.jpg|right|300px|thumb|Goal twoaie ayns spreie [[eas]]]]

== Soilshaghey oaylleeagh ==

Ta soilshey [[aascellaghey]] tra t'eh goll stiagh 'sy vineen. T'eh aahoilshaghey jeh cooyl y vineen, as eisht aascellaghey reesht tra t'eh goll magh ass y vineen. Er y fa dy vel soilshey tonn giare aascellaghey ny smoo na soilshey tonn liauyr, ta'n soilshey eddyrscarrey dys spectrum.<ref>{{enmyseddyrvoggyl
  | kiangley = http://www.physicsclassroom.com/Class/refrn/u14l4b.cfm
  | ennym = Rainbow Formation
  | screeudeyr = Physics Classroom
}}</ref> Ta'n soilshey smoo jeean er uillin mysh 40–42°. T'eh uillin hene croghey er [[ayndagh aahoilshaghey]] y vineen.  Ta ayndagh aahoilshaghey saailley ny smoo na fliaghey, as myr shen ta lieh-chrantessen sloo ec goal twoaie ayns spreie marrey na goal twoaie ayns fliaghey.

[[Coadan:Rainbow1.svg|right|300px|thumb|Ta soilshey bane rheynn ayns "daahghyn" (tonnyn-lhiuridyn) lesh goll stiagh 'sy vineen, er y fa dy vel soilshey "jiarg" (tonn liauyr) aascellaghey er uillin sloo na soilshey "gorrym" (tonn ghiare). Tra t'ad faagail y bineen, ta ny scellyn jiargey er gassey trooid uillin sloo na ny scellyn gorrym, as myr shen ta straih daaghyn ry-akin, jiarg dys gorrym as ny daaghyn elley eddyr oc.]]

<!--[[File:Rainbow single reflection.svg|right|250px|thumb|Light rays enter a raindrop from one direction (typically a straight line from the Sun), reflect off the back of the raindrop, and fan out as they leave the raindrop. The light leaving the rainbow is spread over a wide angle, with a maximum intensity at 40.89–42°.]]
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Cha nel ynnyd er lheh ec goal twoaie 'sy speyr. Ta'n ynnyd baghtal echey croghey er ynnydyn ny greiney as y chronneyder. Ta dagh bineen aascellaghey as aahoilshaghey soilshey ny greiney 'syn aght cheddin, agh cha nel agh beggan jeh'n toilshey roshtyn sooill y chronneyder. She yn soilshey shen ta jannoo magh goal twoaie da'n chronneyder shen. Ta ynnyd goal twoaie 'sy speyr noi y ghrian cosoylit rish y chronneyder, as ta mean y ghoal twoaie erskyn scaa-doo kione y chronneyder, ec yn [[ynnyd noi-ghrianagh]]. Ta'n goal twoaie ry-akin mysh 40–42° jeh linney eddyr kione y chronneyder as scaa-doo y chione. Myr shen, my ta'n ghrian ny s'ardjey na 42°, ta'n goal twoaie fo oirr ny cruinney, as cha nel eh ry-akin mannagh vel y chronneyder fodder erskyn y thalloo.
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==Visibility==
[[File:A surfer in the air 2.jpg|right|300px|thumb|Rainbows may also form in the spray created by waves (called ''spray bows'').]]
Rainbows can be observed whenever there are water [[drop (liquid)|drops]] in the air and [[sunlight]] shining from behind at a low [[altitude]] [[angle]]. The most spectacular rainbow displays happen when half of the sky is still dark with raining [[cloud]]s and the observer is at a spot with clear sky in the direction of the Sun. The result is a luminous rainbow that contrasts with the darkened background.

The rainbow effect is also commonly seen near [[waterfall]]s or [[fountain]]s. In addition, the effect can be artificially created by dispersing water droplets into the air during a sunny day. Rarely, a [[moonbow]], lunar rainbow or nighttime rainbow, can be seen on strongly moonlit nights. As human [[visual perception]] for colour is poor in low light, moonbows are often perceived to be white.<ref>{{cite web |last=Walklet |first=Keith S. |year=2006 |url=http://www.anseladams.com/content/newsletter/lunar_rainbow.html |title=Lunar Rainbows - When to View and How to Photograph a "Moonbow" |publisher=The Ansel Adams Gallery |accessdate=2007-06-07}}</ref> It is difficult to photograph the complete semicircle of a rainbow in one frame, as this would require an [[angle of view]] of 84°. For a [[135 film|35&nbsp;mm]] camera, a lens with a focal length of 19&nbsp;mm or less [[wide-angle lens]] would be required. Now that powerful software for stitching several images into a panorama is available, images of the entire arc and even secondary arcs can be created fairly easily from a series of overlapping frames. From an [[fixed-wing aircraft|aeroplane]], one has the opportunity to see the whole circle of the rainbow, with the plane's shadow in the centre. This phenomenon can be confused with the [[glory (optical phenomenon)|glory]], but a glory is usually much smaller, covering only 5–20°.

At good visibility conditions (for example, a dark cloud behind the rainbow), the second arc can be seen, with inverse order of colours. At the background of the blue sky, the second arc is barely visible.

==Variations==
{| style="margin-left: auto; margin-right: auto;"
|[[File:rainbowrays2.png|right|250px|thumb|Some light reflects twice inside the raindrop before exiting to the viewer. When the incident light is very bright, this can be seen as a secondary rainbow, brightest at 50–53°.]]
|[[File:Regenbogen (NASA).jpg|right|250px|thumb|A double rainbow features reversed colours in the outer (secondary) bow, with the dark [[Alexander's band]] between the bows.]]
|}
Frequently, a dim secondary rainbow is seen outside the primary bow. Secondary rainbows are caused by a double reflection of sunlight inside the raindrops, and appear at an angle of 50–53°. As a result of the second reflection, the colours of a secondary rainbow are inverted compared to the primary bow, with blue on the outside and red on the inside. The secondary rainbow is fainter than the primary because more light escapes from two reflections compared to one and because the rainbow itself is spread over a greater area of the sky. The dark area of unlit sky lying between the primary and secondary bows is called [[Alexander's band]], after [[Alexander of Aphrodisias]] who first described it.

A third, or tertiary, rainbow can be seen on rare occasions, and a few observers have reported seeing quadruple rainbows in which a dim outermost arc had a rippling and pulsating appearance. These rainbows would appear on the same side of the sky as the Sun, making them hard to spot. One type of tertiary rainbow carries with it the appearance of a secondary rainbow immediately outside the primary bow. The closely spaced outer bow has been observed to form dynamically at the same time that the outermost (tertiary) rainbow disappears. During this change, the two remaining rainbows have been observed to merge into a band of white light with a blue inner and red outer band. This particular form of doubled rainbow is not like the classic double rainbow due to both spacing of the two bows and that the two bows share identical normal colour positioning before merging. With both bows, the inner colour is blue and the outer colour is red.

Higher-order rainbows were described by Felix Billet (1808–1882) who depicted angular positions up to the 19th-order rainbow, a pattern he called "rose".<ref>{{Cite journal |url=http://www.numdam.org/item?id=ASENS_1868_1_5__67_0 |title=Mémoire sur les Dix-neuf premiers arcs-en-ciel de l'eau |first=Felix |last=Billet |journal=Annales scientifiques de l'École Normale Supérieure |volume=1 |issue=5 |pages= 67–109 |year=1868 |accessdate=2008-11-25}}</ref> In the laboratory, it is possible to observe higher-order rainbows by using extremely bright and well [[collimated]] light produced by [[laser]]s. A sixth-order rainbow was first observed by K. Sassan in 1979 using a [[HeNe]] laser beam and a pendant water drop.<ref>K. Sassen, J. Opt. Soc. Am. 69 (1979) 1083.</ref> Up to the 200th-order rainbow was reported by Ng et al. in 1998 using a similar method but an argon ion laser beam.<ref>P.H. Ng, M.Y. Tse, and W.K. Lee, ''J. Opt. Soc. Am.'' B 15 (1998) 2782</ref>

===Supernumerary rainbow===
[[File:Supernumerary rainbow 03 contrast.jpg|right|175px|thumb|A contrast-enhanced photograph of a supernumerary rainbow, with additional green and purple arcs inside the primary bow.]]   
A '''supernumerary rainbow'''—also known as a '''stacker rainbow'''—is an infrequent phenomenon, consisting of several faint rainbows on the inner side of the primary rainbow, and very rarely also outside the secondary rainbow. Supernumerary rainbows are slightly detached and have pastel colour bands that do not fit the usual pattern. 

It is not possible to explain their existence using classical geometric [[optics]]. The alternating faint rainbows are caused by [[interference]] between rays of light following slightly different paths with slightly varying lengths within the raindrops. Some rays are in [[phase (waves)|phase]], reinforcing each other through [[constructive interference]], creating a bright band; others are out of phase by up to half a wavelength, canceling each other out through [[destructive interference]], and creating a gap. Given the different angles of refraction for rays of different colours, the patterns of interference are slightly different for rays of different colours, so each bright band is differentiated in colour, creating a miniature rainbow. Supernumerary rainbows are clearest when raindrops are small and of similar size. The very existence of supernumerary rainbows was historically a first indication of the [[wave]] nature of light, and the first explanation was provided by [[Thomas Young (scientist)|Thomas Young]] in 1804.

===Reflected rainbow, reflection rainbow===
[[File:ReflectionRainbow.jpg|right|250px|thumb|Reflection rainbow and normal rainbow, at sunset]]
When a rainbow appears above a body of water, two complementary mirror bows may be seen below and above the horizon, originating from different light paths. Their names are slightly different. A '''reflected rainbow''' will appear as a mirror image in the water surface below the horizon, if the surface is quiet (see photo above). The sunlight is first deflected by the raindrops, and then reflected off the body of water, before reaching the observer. The reflected rainbow is frequently visible, at least partially, even in small puddles.

Where sunlight reflects off a body of water before reaching the raindrops (see [http://www.eo.ucar.edu/rainbows/rnbw8.gif diagram]), it may produce a '''reflection rainbow''' (see photo at the right), if the water body is large, quiet over its entire surface, and close to the rain curtain. The reflection rainbow appears above the horizon. It intersects the normal rainbow at the horizon, and its arc reaches higher in the sky, with its centre as high above the horizon as the normal rainbow's centre is below it. Due to the combination of requirements, a reflection rainbow is rarely visible.

Six (or even eight) bows may be distinguished if the reflection of the reflection bow, and the secondary bow with its reflections happen to appear simultaneously.<ref>{{cite web |author=Terje O. Nordvik |url= http://apod.nasa.gov/apod/ap070912.html |title=Six Rainbows Across Norway |publisher=APOD (Astronomy Picture of the Day) |accessdate=2007-06-07}}</ref>

===Circumhorizontal arc===
The [[circumhorizontal arc]] is sometimes referred to by the misnomer "fire rainbow". As it originates in ice crystals, it is not a rainbow but a [[halo (optical phenomenon)|halo]].<ref name="atoptics-circumhor">{{cite web |url=http://www.atoptics.co.uk/halo/cha2.htm |title=Circumhorizontal arc |author=Les Cowley |publisher=Atmospheric Optics |accessdate=2007-04-22}}</ref>

===Rainbows on Titan===
It has been suggested that rainbows might exist on Saturn's moon [[Titan (moon)|Titan]], as it has a wet surface and humid clouds. The radius of a Titan rainbow would be about 49° instead of 42°, because the fluid in that cold environment is methane instead of water. A visitor might need [[infrared]] goggles to see the rainbow, as Titan's atmosphere is more transparent for those wavelengths.<ref>{{cite web |url= http://science.nasa.gov/headlines/y2005/25feb_titan2.htm |title=Rainbows on Titan |author=Science@NASA |accessdate=2008-11-25}}</ref>

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== Imraaghyn ==
{{rolleyimraaghyn}}

[[Ronney:Phenomena shilleydagh aeraghtagh]]
She phenomenon shilleydagh as emshyragh eh goal twoaie (goll twoaie, Bhow Ghorree). T'eh cur er spectrum sollys çheet rish 'sy speyr tra ta soilshey ny greiney bentyn rish bineenyn ushtey 'syn aeraght. Ta cummey cruillag yl-daahagh echey, as jiarg er y çheu mooie echey, as gorrym-jiarg er y çheu sthie. She spectrum gyn creeaghyn t'ayn, agh ta sleih cliaghtey rheynn eh ayns daahghyn discreajagh. Hug Isaac Newton queig daahghyn da: jiarg, buigh, geayney, gorrym as "violet" (cummey gorrym-jiarg gyn fockle 'sy Ghaelg, myr daah lus y chree). Hug eh stiagh jiarg-bwee as plooreen ny s'anmey rere aarey chiaull.  Cha nel dagh çhengey cur ny daahghyn cheddin da.

Cha nee fliaghey ynrican nod ve ny vun goal twoaie; t'ad ry-akin ayns kay as spreie myrgeddin.

right|300px|thumb|Goal twoaie ayns spreie eas

 Soilshaghey oaylleeagh 

Ta soilshey aascellaghey tra t'eh goll stiagh 'sy vineen. T'eh aahoilshaghey jeh cooyl y vineen, as eisht aascellaghey reesht tra t'eh goll magh ass y vineen. Er y fa dy vel soilshey tonn giare aascellaghey ny smoo na soilshey tonn liauyr, ta'n soilshey eddyrscarrey dys spectrum. Ta'n soilshey smoo jeean er uillin mysh 40–42°. T'eh uillin hene croghey er ayndagh aahoilshaghey y vineen.  Ta ayndagh aahoilshaghey saailley ny smoo na fliaghey, as myr shen ta lieh-chrantessen sloo ec goal twoaie ayns spreie marrey na goal twoaie ayns fliaghey.

right|300px|thumb|Ta soilshey bane rheynn ayns "daahghyn" (tonnyn-lhiuridyn) lesh goll stiagh 'sy vineen, er y fa dy vel soilshey "jiarg" (tonn liauyr) aascellaghey er uillin sloo na soilshey "gorrym" (tonn ghiare). Tra t'ad faagail y bineen, ta ny scellyn jiargey er gassey trooid uillin sloo na ny scellyn gorrym, as myr shen ta straih daaghyn ry-akin, jiarg dys gorrym as ny daaghyn elley eddyr oc.

Cha nel ynnyd er lheh ec goal twoaie 'sy speyr. Ta'n ynnyd baghtal echey croghey er ynnydyn ny greiney as y chronneyder. Ta dagh bineen aascellaghey as aahoilshaghey soilshey ny greiney 'syn aght cheddin, agh cha nel agh beggan jeh'n toilshey roshtyn sooill y chronneyder. She yn soilshey shen ta jannoo magh goal twoaie da'n chronneyder shen. Ta ynnyd goal twoaie 'sy speyr noi y ghrian cosoylit rish y chronneyder, as ta mean y ghoal twoaie erskyn scaa-doo kione y chronneyder, ec yn ynnyd noi-ghrianagh. Ta'n goal twoaie ry-akin mysh 40–42° jeh linney eddyr kione y chronneyder as scaa-doo y chione. Myr shen, my ta'n ghrian ny s'ardjey na 42°, ta'n goal twoaie fo oirr ny cruinney, as cha nel eh ry-akin mannagh vel y chronneyder fodder erskyn y thalloo.

 Imraaghyn 

Ronney:Phenomena shilleydagh aeraghtagh