How do a rainbow get it's colors?

Question

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I typed it wrong but don't want to remove question.

Answer 1

Put simply...
Basically the different colors the make up white light travel at different speeds and when they are bent the sharpness of the turn varies according to the speed. Since all colors travel at different speeds they separte and become visable creating the colors of a rainbow.

In Detail...
The fundamental process at work in a rainbow is refraction -- the "bending" of light.

A prism separates white light into its component colors. Different colors of light have different frequencies, which causes them to travel at different speeds when they move through matter.

A color that travels more slowly in glass will bend more sharply when it passes from air to glass, because the speed difference is more severe. A color that moves more quickly in glass won't slow down as much, so it will bend less sharply.

In this way, the colors that make up white light are separated according to frequency when they pass through glass. If the glass bends the light twice, as in a prism, you can see the separated colors more easily. This is called dispersion.

Drops of rainwater can refract and disperse light in the same basic way as a prism. In the right conditions, this refraction forms rainbows.

Answer 2

A rainbow is the separation of white light into its colored components by refraction through water droplets in the atmosphere.
The colors represent the various frequencies inherent in light.

Answer 3

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Answer 4

First of all the sentence contains grammatical error, it should be, “How does a rainbow get its colors?

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 multicolored arc, with red on the outside and violet on the inside. Even though a rainbow spans a continuous spectrum of colors, traditionally the full sequence of colors is most commonly cited as red, orange, yellow, green, blue, and violet. It is commonly thought that indigo was included due to the different religious connotations of the numbers six and seven at the time of Isaac Newton's work on light, despite its lack of scientific significance and the poor ability of humans to distinguish colors in the blue portion of the visual spectrum.

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

The rainbow's appearance is caused by dispersion of sunlight as it is refracted by (approximately spherical) 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 about 40°-42°. This angle is independent of the size of the drop, but does depend a lot on its shape and refractive index. Due to the surface tension waterdrops are always round and the refractive index of pure water is always 1.33. Seawater, on the other hand has a higher refractive index, which results in a smaller angle. This is easily measurable when a 'rain'bow is created from splashing up seawaves.

Since the water is dispersive, the amount that the sunlight is bent depends upon the wavelength, and hence colour, of the light's constituent parts. Blue light 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; however, light that emerges from the back of the raindrop does not create a rainbow between the observer and the Sun. The 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 and do not form a rainbow.

A rainbow does not actually exist at a location in the sky, but rather is an optical phenomenon whose apparent position depends on the observer's location. All raindrops refract and reflect the sunlight in the same way, but only the light from some raindrops reaches the observer's eye.

These raindrops are perceived to constitute the rainbow by that observer. 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 approximately 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 usually not enough raindrops between the horizon (that is: eye height) and the ground, to contribute.

One exception is when the observer is at the top of a mountain or a similar vantage point, for example an aeroplane (see below). Another exception occurs when the rainbow is produced by a garden sprinkler. Although in this case to get sufficient drops they must be very small, resulting in a quite colourless bow. It is difficult to photograph the complete arc of a rainbow, which 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 airplane, one has the opportunity to see the whole circle of the rainbow, with the plane's shadow in the center. This phenomenon can be confused with the glory, but a glory is usually much smaller, covering only 5°­20°, as opposed to over 80° for a full circle rainbow. Speed and direction of light in materials?


In a vacuum all frequencies of light travel at the same speed but in a material, the speed is reduced.
The ratio of the speed of light in a vacuum, c, to the speed of light in a material, v, is the index of refraction,
n = c / v.n equals about 1.333 in water
The change in speed causes the direction of a light beam to change. There is a relationship between the angles at which light enters and leaves a boundary between materials with different indices of refraction called Snell's law. It is: n1 * sin (theta1) = n2 * sin (theta2)

Variations
Occasionally, a second, dimmer 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.
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.
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.