Since the value of µ for water is about, it follows that n must be at least unity for a rainbow to be formed; there is obviously no theoretical limit to the value of n, and hence rainbows of higher orders are possible.
Water shot from the bottom of the canyon, forming hundreds of tall columns whose mist cast rainbows in the bright moonlight.
The moon can produce rainbows in the same manner as the sun.
Intersecting rainbows are sometimes observed.
PerEwpa, literally " things in the air," from yerb., beyond, and a€ipav, to lift up), a term originally applied by the ancient Greeks to many atmospheric phenomena - rainbows, halos, shooting stars, &c. - but now specially restricted to those luminous bodies known as shooting stars, falling stars, fireballs and bolides.
The Vernal, about half a mile below the Nevada, is famous for its afternoon rainbows, At flood-time it is a nearly regular sheet about 80 ft.
In the first class we have halos, and coronae, or "glories," which encircle the luminary; the second class includes rainbows, fog-bows, mist-halos, anthelia and mountainspectres, whose centres are at the anti-solar point.
The impurity of the colours (due partly to the sun's diameter, but still more to oblique refraction) is more marked in halos than in rainbows; in fact, only the red is at all pure, and as a rule, only a mere trace of green or blue is seen, the external portion of each halo being nearly white.
Formerly classified by the ancient Greeks with halos, rainbows, &c., under the general group of "meteors," they came to receive considerable attention at the hands of Descartes, Christiaan Huygens, and Sir Isaac Newton; but the correct explanation of coronae was reserved until the beginning of the 19th century, when Thomas Young applied the theories of the diffraction and interference of light to this phenomenon.
John Fleischer (sometimes incorrectly named Fletcher), of Breslau, propounded the same view in a pamphlet, De iridibus doctrina Aristotelis et Vitellonis (1574) the same explanation was given by Franciscus Maurolycus in his Photismi de lumine et umbra (1575) The most valuable of all the earlier contributions to the scientific explanation of rainbows is undoubtedly a treatise by Marco Antonio de Dominis (1566-1624), archbishop of Spalatro.
He attempted, not without success, to give a scientific account of eclipses, meteors, rainbows and the sun, which he described as a mass of blazing metal, larger than the Peloponnesus; the heavenly bodies were masses of stone torn from the earth and ignited by rapid rotation.