My son asked me "what is a rainbow made of"?????

Question

His dad said lots of differant colours.
I didnt have a better answer,
so i kept my mouth shut.
But he would still like to know

Answer 1

rainbow is an optical and meteorological phenomenon that causes a nearly continuous spectrum of light to appear in the sky when the Sun shines onto droplets of moisture in the Earth's atmosphere. It takes the form of a multicoloured arc, with red on the outside and violet on the inside. More rarely, a double rainbow is seen, which includes a second, fainter arc with colours in the opposite order, that is, with violet on the outside and red on the inside.

Even though a rainbow spans a continuous spectrum of colours, traditionally the full sequence of colours is most commonly cited and remembered as red, orange, yellow, green, blue, indigo and violet. ("Roy G. Biv" and "Richard Of York Gave Battle In Vain" are popular mnemonics.)

Though rainbows are bow-shaped in most cases, there are also phenomena of rainbow-colored strips in the sky: in the shape of stripes, circles, or even flames. (See Circumhorizontal arc)

Contents [hide]
1 Scientific explanation
2 Variations
3 History of the science of rainbows
4 Rainbows in culture
4.1 Rainbows in religion and mythology
4.2 Rainbows in art and photography
4.3 Rainbows in literature
4.4 Rainbows in popular culture
5 The sequence of colours
6 See also
7 Notes
8 References
9 External links



[edit] Scientific explanation

Rainbows may also form in mist, such as that of a waterfallRainbows can be observed whenever there are water drops in the air and sunlight shining from behind the observer at a low altitude or angle. The most spectacular rainbow displays when half of the sky is still dark with draining clouds and the observer is at a spot with clear sky overhead. The rainbow effect is also commonly seen near waterfalls or fountains. Rainbow fringes can sometimes be seen at the edges of backlit clouds and as vertical bands in distant rain or virga. The effect can also be artificially created by dispersing water droplets into the air during a sunny day.

Rarely, a moonbow, or night-time rainbow, can be seen on strongly moonlit nights. As human visual perception for colour is poor in low light, moonbows are most often perceived to be white.

The rainbow's appearance is caused by dispersion of sunlight as it goes through raindrops. The light is first refracted as it enters the surface of the raindrop, reflected off the back of the drop, and again refracted as it leaves the drop. The overall effect is that the incoming light is reflected back over a wide range of angles, with the most intense light at an angle of 40°–42°. The angle is independent of the size of the drop, but does depend on its refractive index. Seawater has a higher refractive index than rain water, so the radius of a 'rain'bow in sea spray is smaller than a true rainbow. This is visible to the naked eye by a misalignment of these bows.[1]

The amount by which light is refracted depends upon its wavelength, and hence its color. Blue light (shorter wavelength) is refracted at a greater angle than red light, but because the area of the back of the droplet has a focal point inside the droplet, the spectrum crosses itself, and therefore the red light appears higher in the sky, and forms the outer colour of the rainbow. Contrary to popular belief, the light at the back of the raindrop does not undergo total internal reflection and some light does emerge from the back. However, light coming out the back of the raindrop does not create a rainbow between the observer and the sun because spectra emitted from the back of the raindrop do not have a maximum of intensity, as the other visible rainbows do, and thus the colours blend together rather than forming a rainbow.


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 of 40.6°–42°.
White light separates into different colours (wavelengths) on entering the raindrop because red light is refracted by a lesser angle than blue light. On leaving the raindrop, the red rays have turned through a smaller angle than the blue rays, producing a rainbow.

A rainbow does not actually exist at a particular location in the sky. It is, instead, an optical phenomenon whose apparent position depends on the observer's location and the position of the sun. All raindrops refract and reflect the sunlight in the same way, but only the light from some raindrops reaches the observer's eye. This light is what constitutes the rainbow for that observer.


A portion of a 360 degree rainbow, seen from an aeroplane.The position of a rainbow in the sky is always in the opposite direction of the Sun with respect to the observer, and the interior is always slightly brighter than the exterior. The bow is centred on the shadow of the observer's head, or more exactly at the antisolar point (which is below the horizon during the daytime), appearing at an angle of 40°–42° to the line between the observer's head and its shadow. As a result, if the Sun is higher than 42°, then the rainbow is below the horizon and cannot be seen as there are not usually sufficient raindrops between the horizon (that is: eye height) and the ground, to contribute. Exceptions occur when the observer is high above the ground, for example in an aeroplane (see below), on top of a mountain, or above a waterfall. A rainbow can be generated using a garden sprinkler but to get sufficient drops they must be very small.

It is difficult to photograph the complete arc of a rainbow, as this would require an angle of view of 84°. For a 35 mm camera, a lens with a focal length of 19 mm or less would be required, whilst most photographers are only likely to have a 28 mm wide-angle lens. From an 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, but a glory is usually much smaller, covering only 5°–20°.


[edit] Variations
Occasionally, a second, dimmer, and thicker 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 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.


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°.
A double rainbow features reversed colours in the outer (secondary) bow, with the dark Alexander's band between the bows.


A contrast-enhanced photograph of a supernumerary rainbow, with additional green and purple arcs inside the primary bow.
Primary and secondary rainbows are visible, as well as a reflected primary and a faintly visible reflected secondary.A third, or triple, 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.

Occasionally, another beautiful and striking rainbow phenomenon can be observed, consisting of several faint rainbows on the inner side of the primary rainbow, and very rarely also outside the secondary rainbow. They are slightly detached and have pastel colour bands that do not fit the usual pattern. They are known as supernumerary rainbows, and 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, reinforcing each other through constructive interference, creating a bright band; others are out of phase by up to half a wavelength, cancelling 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 in 1804.

Other rainbow variants are produced when sunlight reflects off a body of water. Where sunlight reflects off water before reaching the raindrops, it produces a reflection rainbow. These rainbows share the same endpoints as a normal rainbow but encompass a far greater arc when all of it is visible. Both primary and secondary reflection rainbows can be observed.

A reflected rainbow, by contrast, is produced when light that has first been reflected inside raindrops then reflects off a body of water before reaching the observer. A reflected rainbow is not a mirror image of the primary bow, but is displaced from it to a degree dependent on the Sun's altitude. Both types can be seen in the image to the right.


[edit] History of the science of rainbows

René Descartes' sketch of how primary and secondary rainbows are formedThe Persian astronomer Qutb al-Din al-Shirazi (1236–1311), or perhaps his student Kamal al-din al-Farisi (1260–1320), is thought to have first given a fairly accurate explanation for the rainbow phenomenon.[2] The work of Robert Grosseteste on light was continued by Roger Bacon, who wrote in his Opus Majus of 1268 about experiments with light shining through crystals and water droplets showing the colours of the rainbow. Theodoric of Freiberg is also known to have given an accurate theoretical explanation of both the primary and secondary rainbows in 1307. He explained the primary rainbow, noting that "when sunlight falls on individual drops of moisture, the rays undergo two refractions (upon ingress and egress) and one reflection (at the back of the drop) before transmission into the eye of the observer".[3] He explained the secondary rainbow through a similar analysis involving two refractions and two reflections.

Descartes, in 1637, further advanced this explanation. Knowing that the size of raindrops did not appear to affect the observed rainbow, he experimented with passing rays of light through a large glass sphere filled with water. By measuring the angles that the rays emerged, he concluded that the primary bow was caused by a single internal reflection inside the raindrop and that a secondary bow could be caused by two internal reflections. He was able to back this up with a derivation of the law of refraction (subsequently, but independently of, Snell) and correctly calculated the angles for both bows. His explanation of the colours, however, was based on a mechanical version of the traditional theory that colours were produced by a modification of white light.

Isaac Newton was the first to demonstrate that white light was composed of the light of all the colours of the rainbow, which a glass prism could separate into the full spectrum of colours, rejecting the theory that the colours were produced by a modification of white light. He also showed that red light gets refracted less than blue light, which led to the first scientific explanation of the major features of the rainbow. Newton's corpuscular theory of light was unable to explain supernumary rainbows, and a satisfactory explanation was not found until Thomas Young realised that light behaves as a wave under certain conditions, and can interfere with itself.

Young's work was refined in the 1820s by George Biddell Airy, who explained the dependence of the strength of the colours of the rainbow on the size of the water droplets. Modern physical descriptions of the rainbow are based on Mie scattering, work published by Gustav Mie in 1908. Advances in computational methods and optical theory continue to lead to a fuller understanding of rainbows. For example, Nussenzveig provides a modern overview.[4]


[edit] Rainbows in culture

[edit] Rainbows in religion and mythology

The end of a rainbow.Main article: Rainbows in mythology
The rainbow has a place in legend due to its beauty and the difficulty in explaining the phenomenon before the work of Descartes in the 17th century (although, as mentioned above, Theodoric of Freiburg had given a satisfactory explanation in the 13th century.)

In Greek mythology, the rainbow was considered to be a path made by a messenger (Iris) between Earth and Heaven. In Chinese mythology, the rainbow was a slit in the sky sealed by Goddess Nüwa using stones of five different colours. In Hindu mythology, the rainbow is called Indradhanush, meaning the bow of Indra, the God of lightning and thunder.


A coloured woodcut from the Nuremberg Chronicles shows a rainbow with the 12 signs of the zodiac.In Norse Mythology, a rainbow called the Bifröst Bridge connects the realms of Ásgard and Midgard, homes of the gods and humans, respectively. The Irish leprechaun's secret hiding place for his pot of gold is usually said to be at the end of the rainbow (which is impossible to reach).

In the Bible, the rainbow is a symbol of the covenant between God and man, and God's promise to Noah that he would never again flood the entire Earth. The Rainbow has even become the symbol for a modern movement within Judaism called B'nei Noah. B'nei Noah are non-Jews who continue to follow in the ways of their ancestor Noah. The Noahide movement has its roots in Jewish Tradition, specifically the Talmud. The rainbow body is an important concept in Tibetan Buddhism.


[edit] Rainbows in art and photography
A number of painters have depicted the rainbow. Frequently these have a symbolic or programmatic significance. (See, for example, Albrecht Dürer's Melancholia I.) In particular, the rainbow often appears in religious art. (See Joseph Anton Koch's Noah's Thanksoffering and Roger van der Weyden's Last Judgment shown below.) However, Romantic landscape painters such as J. M. W. Turner and John Constable have been more concerned with recording fleeting effects of light. (See, for example, Constable's Salisbury Cathedral from the Meadows.) Other notable examples appear in work by Hans Memling, Caspar David Friedrich, and Peter Paul Rubens.

The rainbow is a favourite subject for photographers, to such an extent that photographs of rainbows seem to be more commonplace than rainbows themselves. Occasionally, a rainbow photo will be surprisingly artistic and beautiful, as Georges Noblet's "Harpe de Lumière" shown below

Answer 2

When tiny raindrops are so small they can float in the air, then when the sunlight shines through them the light is split into the different colours that actually make up sunlight.
Each tiny raindrop is very small and doesn't split much light, but there are so many drops that their effects all add up to the rainbow.
You can see the same effect if you have a hose spraying a fine mist of water when you water the lawn and the sun shines through the mist at just the right angle.
Same thing happens if you have a crystal of the right shape hanging in a window and the sunlight shines through it - you'll see a rainbow on the wall.

Answer 3

white light is made up of numerous colours. These colours are called the spectrum. Starting with invisible light there is infared. Then onto visible light. Red, green and blue. As these colours merge, you get orange, for example, in between red and green. Then there is another invisible light, ultraviolet. This is sometimes visible as it contains a mix of blue and ultraviolet light, blue being visible giving a purple colour due to the mixing. When light is passed through a prism, it can be split up into these different colours. A raindrop acts like a prism, splitting up the white light from the sun into the colours of the spectrum. With the millions of raindrops in the sky, the spectrum colours become clearly visible in the middle of the sky, causing whats known as a rainbow. Hope this helps

Answer 4

Moisture in the air is the simple answer.

If you remember from highschool white light is composed of all the colours in he rainbow (red, orange, yellow, green, blue, indigo, violet (in that order)). You can see this if you take something like a prism and shine white light through it. The light will separate into its individual bands of

After rainfall there tends to be a lot of moisture in the air (droplets of water). This moisture does the same thing as the prism. It takes the light (obviously coming from teh sun :P) and breaks it into its individual colours.

One other point is that when you make a "rainbow" at home by using a prism and some light you see the rainbow on the wall.

You might be thinking, "what the heck, the real rainbows i see are in the sky....there's no walls up there"

The huge amount of moisture in the air can also act as a wall. So the moisture bends the white light into its individual colours and then projects them onto other droplets of water in the air.

Done and done

Answer 5

A rainbow is made by white light (the light around us everyday) passing through the rain drops, which act as a prism. When the light passes through the rain drops is splits into the spectrum Red Orange Yellow Green Blue Indigo and Violet. Each of these has a different wave length which means they "bend" in different amounts which cause the rainbow. This is called dispersion.
If you want to show your son that light is made of different colours at home, cut a circular piece of paper and divide it into 7 equal sections, colour each of the section in the colours of the spectrum. Put two holes in the middle of the circle, thread some string through the holes so the circle is in the middle of the string. Turn the string and pull so the circle spins. The colours merge into white, like light :-)
Hope it helps

Answer 6

Dad was not far off (however, he was quite unclear as to why his definition was not bad).

Rainbow is made of sunlight that is refracted by drops of water. As the white light of the sun enters a rain drop, bounces around the inside "face" of the drop and exits again, we note two things:

1) The angle of exit is approximately 42 degrees away from the direction that the light came in. So, turning your back to the sun, the circle should make an apparent radius of 42 degrees in the sky, with the centre being exactly opposite the sun -- i.e., the centre of the circle is the shadow of your head.
This explains why rainbows are not seen in the sky when the Sun is higher than 42 degrees above the horizon (the entire rainbow would be below the horizon).

2) Different colours are refracted slightly differently when inside the water (this is true in any refraction, whether the medium be water, glass, a transparent mineral or a grating, as on the surface of CD or DVD).

So, with your back to the sun, looking towards where there is a rain shower, you will see blue light where the raindrops are located a little less than 42 degrees from the centre of the rainbow (the shadow of your head) and red where the raindrop is a little more than 42 degrees away from the centre. And, of course, all colours in between are... in between.

The exact angle at which the light comes out of the raindrop after bouncing around inside, depends on the number of bounces. Most light will come out after one bounce (refracted upon entering, bounce on the "back" of the drop, refract on the way out) for a total turn around angle of 138 degrees (180 - 42).

Some photons will bounce around twice and come out at a larger angle (covering 50 to 53). The double bounce inverts the effect of refraction and, in this secondary rainbow, always fainter than the main one, red is inside and blue is outside. The secondary rainbow is outside the main rainbow; it appears larger in size, but is always fainter.

Multiple bounces are rarer but they do happen. So it is possible to see even more bows, but they will almost always be fainter than the main one. Of course, if there are no drops in the direction of 42 degrees away from the anti-sun direction (shadow of your head), then there is no main rainbow and it is possible that you see a minor rainbow from another direction. This would be rare.

Answer 7

Tell him that in the bible, one of those days, the sun was out and it rained, and across the sky on top of the mountain a rainbow appeared, the wise men and everyone living in bibligal times, were appalled and soo much in ahhhh, that their sprits became alive, and they all felt at ease looking at this beautiful scene, They called it a rainbow, And that story is also, in a true book about the american Indian also, not in soo many words though

Answer 8

First, show your son a picture of light passing through a prism. Point out to him the different colors that come out of the prism. There's a dandy photo of all that on this website ==>http://www.fotosearch.com/AGE030/c47-381401/
Next, explain to him that each and every falling raindrop works just like the prism, and since there are millions of rain drops the sky gets filled with an arch of color.

Answer 9

It occurs when water particles in the air act as a prism and bend the rays of light revealing the different spectrums of light in the sun and making them visible, thus producing the various colors of the rainbow.

Answer 10

Light! Light shining through raindrops.

Cool thing I saw recently ... on a day last week, shortly after noon, when the sun was shining through some high thin clouds, there was a rainbow colored ring completely around the sun. Very pretty!

Answer 11

For other uses, see Rainbow (disambiguation).

Full featured rainbow in Wrangell-St. Elias National Park, Alaska.A rainbow is an optical and meteorological phenomenon that causes a nearly continuous spectrum of light to appear in the sky when the Sun shines onto droplets of moisture in the Earth's atmosphere. It takes the form of a multicoloured arc, with red on the outside and violet on the inside. More rarely, a double rainbow is seen, which includes a second, fainter arc with colours in the opposite order, that is, with violet on the outside and red on the inside.