Rainbow (World of Earth Science)
Water droplets and light form the basis of all rainbows, which are circular arcs of color with a common center. Because only water and light are required for rainbows, one will see them in rain, spray, or even fog.
A raindrop acts like a prism and separates sunlight into its individual color components through refraction, as light will do when it passes from one medium to another. When the white light of the Sun strikes the surface of the raindrop, the light waves are bent to varying degrees depending on their wavelength. These wavelengths are reflected on the far surface of the water drop and will bend again as they exit. If the light reflects off the droplet only once, a single rainbow occurs. If the rays bounce inside and reflect twice, two rainbows will appear: a primary and a secondary. The second one will appear fainter because there is less light energy present. It will also occur at a higher angle.
Not all the light that enters the raindrop will form a rainbow. Some of the light, that which hits the droplet directly at its center, will simply pass through the other side. The rays that strike the extreme lower portions of the drop will produce the secondary bow, and those that enter at the top will produce the primary bow.
The formation of the arc was first discussed by Rene Descartes in 1637. He calculated the deviation for a ray of red light to be about 138 degrees. Although light rays may exit the drop in more than one direction, a concentration of rays emerges near the minimum deviation from the direction of the incoming rays. Therefore the viewer sees the highest intensity looking at the rays that have minimum deviation, which form a cone with the vertex in the observer's eye and with the axis passing through the Sun.
The color sequence of the rainbow is also due to refraction. It was Sir Isaac Newton, however, 30 years after Descartes, who discovered that white light was made up of different wavelengths. Red light, with the longest wavelength, bends the least, while violet, being the shortest wavelength, bends the most. The vertical angle above the horizon will be a little less than 41° for the violet (about 40°) and a little more for the red (about 42°). The secondary rainbow has an angular radius of about 50° and its color sequence is reversed from the primary. It is universally accepted that there are seven rainbow colors, which appear in the order: red, orange, yellow, green, blue, indigo, and violet. However, the rainbow is a whole continuum of colors from red to violet and even beyond the colors that the eye can see.
Supernumerary rainbows, faintly colored rings just inside of the primary bow, occur due to interference effects on the light rays emerging from the water droplet after one internal reflection.
No two people will see the same rainbow. If one imagines herself or himself standing at the center of a cone cut in half lengthwise and laid on the ground flatside down, the raindrops that bend and reflect the sunlight that reach the person's eye as a rainbow are located on the surface of the cone. A viewer standing next to the first sees a rainbow generated by a different set of raindrops along the surface of a different imaging cone.
Using the concept of an imaginary cone again, a viewer could predict where a rainbow will appear by standing with his back to the sun and holding the cone to his eye so that the extension of the axis of the cone intersects the Sun. The rainbow will appear along the surface of the cone as the circular arc of the rainbow is always in the direction opposite to that of the Sun.
A rainbow lasts only about a half-hour because the conditions that create it rarely stay steady much longer than this. In many locations, spring is the prime rainbow-viewing month. Rainfall is usually more localized in the spring, and brief showers over limited areas are a regular feature of atmospheric behavior. This change is a result of the higher springtime sun warming the ground more effectively than it did throughout the previous winter months. This process produces local convection. These brief, irregular periods of pre cipitation followed by sunshine are ideal rainbow conditions. Also, the Sun is low enough for much of the day to allow a rainbow to appear above the horizonhe lower the sun, the higher the top of a rainbow.
The "purity" or brightness of the colors of the rainbow depends on the size of the raindrops. Large drops or those with diameters of a few millimeters create bright rainbows with well-defined colors; small droplets with diameters of about 0.01 mm produce rainbows of overlapping colors that appear nearly white.
For refraction to occur, the light must intersect the raindrops at an angle. Therefore no rainbows are seen at noon when the sun is directly overhead. Rainbows are more frequently seen in the afternoon because most showers occur in midday rather than morning. Because the horizon blocks the other half of a rainbow, a full 360° rainbow can only be viewed from an airplane.
The sky inside the arc will appear brighter than that surrounding it because of the number of rays emerging from a raindrop at angles smaller that those that are visible. But there is essentially no light from single internal reflections at angles greater than those of the rainbow rays. In addition to the fact that there is a great deal of light directed within the arc of the bow and very little beyond it, this light is white because it is a mixture of all the wavelengths that entered the raindrop. This is just the opposite in the case of a secondary rainbow, where the rainbow ray is the smallest angle and there are many rays that emerge at angles greater than this one. A dark band forms where the primary and secondary bows combine. This is known as the Alexander's Dark Band, in honor of Alexander of Aphrodisias who discovered this around 200 B.C.
If a viewer had a pair of polarizing sunglasses, he or she would see that light from the rainbow is polarized. Light vibrating horizontally at the top of the bow is much more intense than the light vibrating perpendicularly to it across the bow and it may be as much as 20 times as strong.
Although rare, a full moon can produce a lunar rainbow when it is bright enough to have its light refracted by raindrops just as is the case for the Sun.
See also Electromagnetic spectrum
Rainbow (Contemporary Musicians)
Rainbow began when Ritchie Blackmore, a classically trained and legendarily difficult lead guitarist left Deep Purple, the British heavy metal band that made him famous. The rest of Deep Purple had had the audacity to demand democracynd wouldn't record one of Blackmore's favorite songs, Quatermass's "Black Sheep of the Family"o the guitarist packed up his strings and went solo. He immediately commandeered a New York band, Elf, which had opened for Deep Purple and starred shrieking vocalist Ronnie James Dio. The new band, Rainbow, became a revolving door of over-the-top metal talent.
Although it never had a gold album or a hit single, Rainbow wasn't a failure; the band toured successfully for almost a decade beginning in the mid-1970s and released the underrated metal anthems "Man on the Silver Mountain," "Since You Been Gone" and "Jealous Lover." It also anticipated two major 1980s hard-rock trends: hair bands such as Poison and Bon Jovi, who borrowed aspects of their coiffure and singing styles from Dio, and fast-fingered guitarists such as Yngwie Malmsteen and Joe Satriani, who adapted Blackmore's classical leanings and rock excess. But even Rainbow's members knew they weren't exactly making musical history. "It was successful, but it was always a second-rank band. It never seemed to get any better," bassist Roger Glover told the Los Angeles Times in 1985, after a Deep Purple reunion signaled the end of Rainbow, at least for the time being. "Ritchie and I were getting bored with it."
Born in England, Blackmore began his music studies at age eleven, when his father bought him a guitar and demanded that he take lessons. The British rock scene was just heating up in those days, with eventual contemporaries Jeff Beck, Eric Clapton, and Jimmy Page preparing to form their own bands. Blackmore found work as a session musician. He backed rockabilly heroes Gene Vincent and Jerry Lee Lewis onstage and attended studio sessions by the great freaked-out producer Joe Meek. In 1968 he cofounded Deep Purple, whose first hits were souped-up versions of Joe South's "Hush" and Neil Diamond's "Kentucky Woman." Blackmore soon invented one of the most recognizable metal riffs of all time, "Smoke on the Water," a number-four hit that helped the band sell 15 million records by the mid-1970s.
"Pound for pound, [Blackmore is] one of the best soloists in history, but he's such ad that he'll probably never get the credit he deserves," Billy Corgan, the Smashing Pumpkins' lead singer and guitarist, told Guitar Player in 1996. It was this arrogance that led him to form Rainbow. The band immediately made Black-more happy by covering "Black Sheep of the Family"; they then went to Germany's Musicland Studios to record Ritchie Blackmore's Rainbow. The album's creative axis was Blackmore and Dio, who bonded over a mutual love for both heavy rock and medieval music. "Man on the Silver Mountain," Dio's signature song during his brief Rainbow tenure was the epitome of this Jethro Tull-like concept.
Fans of Blackmore and Dio say the next album, 1976's Rising, was the band's peak, with former Jeff Beck group drummer Cozy Powell (later of Whitesnake and Emerson, Lake, and Powell), then-unknown bassist Jimmy Bain, and keyboardist Tony Carey replacing the original Elf core. The album's core is "Stargazer," an eight-minute dungeons-and-dragons epic featuring busy drumming, a long guitar solo, lyrics about whips, chains, towers of stone and the immortal line "there's no sun in the shadow of the wizard/see how he glides/why, he's lighter than air/oh, I see his face." The album had its less-busy side, too, with the femme-fatale rocker "Starstruck" showing a more restrained Black-more and Powell. In 1981 Kerrang! magazine readers named Rising the greatest metal album of all time.
After a sold-out European tour and live album, Dio stayed on for one more studio round, resulting in 1978's Long Live Rock 'n' Roll, which featured the same mixture of motorcycle-groove metal (the title track) and medieval excess ("Gates of Babylon"). Blackmore tinkered with the band lineup again, replacing bass and keyboard players for the third time in as many albums. As was often the case with Blackmore's bandmates, however, Dio became disenchanted. The guitarist, emboldened by the success of the "Long Live Rock 'n' Roll" single, wanted to move in a more mainstream-rock direction, while Dio preferred to stick with the medieval experiments. He was also tired of deferring to Blackmore. When singer Ozzy Osbourne quit the pioneering Black Sabbath in 1979, Dio landed a job as the future bat-biter's replacement.
Rainbow persevered. For the group's next album, Down to Earth, Blackmore hired bassist Roger Glover and singer Joe Lynn Turner, who exerted a streamlining influence. Although Dio (and perhaps even Black-more) would disagree, the band turned out its best singles, "Since You Been Gone" and "Jealous Lover," both of which sounded great next to Foreigner and REO Speedwagon on early 1980s rock radio. Glover and Turner managed to hang on for the next several years, until Deep Purple reunited in the mid-1980s and Blackmore broke up Rainbow. Before that happened, though, the band had a bombastic finale: their last performance at Tokyo's Budokan Hall in April of 1984 that featured "Difficult to Cure," a rewrite of Beethoven's Ninth Symphony. The song landed on Rainbow's Finyl Vinyl compilation two years later.
The Purple reunion was short-lived, of course, after Blackmore characteristically ripped Gillan in public, calling the singer's attitude unprofessional and his voice, as quoted in Guitar Player, "completely shot." In 1995 Blackmore reunited Rainbow, with two new unknown singers, Dookie White and Candice Night (Blackmore's fiancée), but the moment had passed. By then, Nirvana and other Seattle grunge bands favoring punk simplicity over metal excess were hugely popular, while classically trained metal guitarists were This Is Spinal Tap clichés. Rainbow survived a few more years in that configuration, until Blackmore shifted almost exclusively to his New-Age-y solo project, Blackmore's Night. He also contributed the guitar solos to Pat Boone's "Smoke on the Water" cover on a bizarrely funny solo CD In a Metal Mood. Blackmore's Night, starring Blackmore and Night, continues to tour the world; Shadow of the Moon went gold in Japan.
Ritchie Blackmore's Rainbow, Polydor, 1975.
Rising, Polydor, 1976.
On Stage, Polydor, 1977.
Long Live Rock 'n' Roll, Polydor, 1978.
Down to Earth, Polydor, 1979.
Difficult to Cure, Polydor, 1981.
Bent Out of Shape, Polydor, 1983.
Finyl Vinyl, Polydor, 1986.
Very Best of Rainbow, Chronicles/Polydor, 1997.
Best of Rainbow: The Millennium Collection, Polydor/Universal, 2000.
Graff, Gary, and Daniel Durchholz, editors, MusicHound Rock: The Essential Album Guide, Visible Ink Press, 1999.
Romanowski, Patricia, and Holly George-Warren, Rolling Stone Encyclopedia of Rock & Roll, Rolling Stone Press, 2001.
Boston Globe, April 9, 1987.
Guitar Player, November 1993; December 1996.
Los Angeles Times, January 13, 1985; January 27, 1985.
"Rainbow," All Music Guide, http://www.allmusic.com (October 7, 2002).
Ritchie Blackmore and Blackmore's Night Official Website, http://www.blackmoresnight.com/ritchie_bio.html (October 7, 2002).
Additional information was obtained from the Very Best of Rainbow liner notes, Chronicles/Polydor, 1997.