"Arainbow 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. "
2006-10-04 02:41:38
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answer #1
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answered by Joe the answer man 4
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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. A double rainbow includes a second, fainter, arc with colors in the opposite order.
Even though a rainbow spans a continuous spectrum of colours, traditionally the full sequence of colours is most commonly cited as red, orange, yellow, green, blue, indigo 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 colours in the blue portion of the visual spectrum.
Scientific explanation
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 on its refractive index. As seawater has a higher refractive index than rain water, the radius of a 'rain'bow in a sea spray is smaller than a true rainbow. This is visible to the naked eye by a misalignment of these bows [1].
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 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°, as opposed to over 80° for a full circle rainbow.
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2006-10-04 09:49:53
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answer #2
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answered by catzpaw 6
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Rainbows are made up of millions and millions of tiny little droplets of water (water vapor) which, when the sunlight shines through them, produce a prismatic effect to a viewer on the other side of the cloud of vapor. Look at a glass prism sometime and observe the way sunlight is broken into a fantastic spread of colored light after it passes through the prism. That is what happens when the sunlight passes through all those tiny water droplets.
2006-10-05 09:21:55
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answer #3
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answered by zahbudar 6
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A rainbow is an arch of light exhibiting the spectrum colors in their order, caused by drops of water falling through the air. It is seen usually in the sky opposite to the sun at the close of a shower and also in the spray of waterfalls.
2006-10-04 09:45:33
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answer #4
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answered by dsd 5
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Rainbows are made up of tiny droplets of water suspended in the air. They work like prysms to sperate white light into its' constituant parts.
2006-10-04 10:43:25
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answer #5
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answered by boyfriend_love_jessica 2
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Whenever a person turns gay, a rainbow is born.
Scientific fact!
2006-10-04 10:24:01
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answer #6
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answered by Glockmeister 2
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light which has passed through droplets of water in the air (rain) this acts like a prism splitting the light up into all the different colors.
2006-10-04 12:58:43
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answer #7
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answered by pss4dm 1
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rainbow is a spectrum of light.
when it rains,tiny droplets of water reflect the light rays falling on them and then the white light splits into its seven colours----called VIBGYOR.
2006-10-04 09:48:18
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answer #8
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answered by iRock 5
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it's the electromagnetic spectrum that lets u see rainbows
2006-10-04 09:44:29
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answer #9
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answered by Shastacia J 1
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Refraction of light through vapor in the atmosphere.
2006-10-04 09:52:59
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answer #10
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answered by Anonymous
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