Why rainbow takes the shape of an arch?
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A rainbow is seen when the Sun is behind you and water is in the air in front of you. You can make one with a water hose or maybe see one in the air with rain in the area. Natural rainbows appear very large and several miles away. The top is all you can see because the ground in front of you blocks the lower portion of the rainbow. However, when seen from an airplane, rainbows are complete circles.
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A rainbow (also known as a rainboner) is an optical and meteorological phenomenon that causes a nearly continuous spectrum of light to appear in the sky when the sun shines onto falling rain. It is a multicoloured arc with red on the outside and violet on the inside. The full sequence of colours is red, orange, yellow, green, blue and indigo violet. An easy way to remeber the colors is the name Roy G Biv
160214
They also occur as a circle, if you're in a plane (i was in a microlight) above mist/cloud it's the most spectacular sight, I looked down and there was a circular rainbow. It has to do with the fact that you're viewing it from one point, all the rainbow is relative to you.
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Well.. you say white light it's not refracted by glass... Then if that's true, there shouldn't be a rainbow EVER, no?\nThat's the point, white light it's composed by several colors, that's why it's white. When it goes through a glass, it WILL be refracted, causing it to separate into different spectres of light. Of course, only a minimal part of it will be refracted, for those glasses are constructed in such a way to prevent it from doing so.
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Rainbows are caused by sunlight reflecting off and refracting through raindrops. There is a very specific angle that each different wavelength of light will take so all parts of the rainbow of that color are always seen at exactly that angle away from the Sun, about 42 degrees for visible light. In math, the collection of all points at a certain distance from a point is a circle, so rainbows are seen as a circle around the sun.
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Umm.. No. Rainbows are a result of atmospheric moisture and light, not a short Irish man who tricks kids into buying overpriced cereal.
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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.\n\nEven 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.\n\nScientific explanation\n\nThe 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.\n\nIn 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.\nRainbows may also appear in the spray of a water fountain\nEnlarge\nRainbows may also appear in the spray of a water fountain\n\nThe 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].\n\nSince 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.\n\nA 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 obser
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A rainbow occurs when sunlight passes through sheets of falling rain which act as a prism to separate the light into it's full spectrum of colors. A double rainbow occurs when there are multiple sheets of rain that are perhaps angled slightly differently. One sheet of rain bends the light into one rainbow, the other sheet of rain bends the light in a slightly different path to create a second prismatic display. \n\nBasically, it is like haveing one light source (the sun) and two separate prisms set next to each other, but at slightly different angle giving you two separate spectra or rainbows.\n\nDouble rainbows are very cool indeed. I saw one last summer!
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A full moon can form a rainbow - usually called a "moonbow". It looks kind of grey though.
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A rainbow is formed when sunlight passes through water droplets.  The light is bent allowing the entire color spectrum to be visible.  The color spectrum is always present, but not always visible to the naked eye.  A prism also produces the same effect as it also bends the light allowing the color spectrum to be visible  This is also why the sky is blue.  The light is bent as it passes through the atmosphere and allowing the color blue to be visible to the naked eye.  This process is know as refraction.
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Its the refraction of light, through water droplets. Rainbows can only be seen when the sun is at your back or behind you.
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Sometimes we see two rainbows at once, what causes this? We have followed the path of a ray of sunlight as it enters and is reflected inside the raindrop. But not all of the energy of the ray escapes the raindrop after it is reflected once. A part of the ray is reflected again and travels along inside the drop to emerge from the drop. The rainbow we normally see is called the primary rainbow and is produced by one internal reflection; the secondary rainbow arises from two internal reflections and the rays exit the drop at an angle of 50 degrees° rather than the 42°degrees for the red primary bow. Blue light emerges at an even larger angle of 53 degrees°. his effect produces a secondary rainbow that has its colors reversed compared to the primary, as illustrated in the drawing, adapted from the Science Universe Series Sight, Light, and Color. \nIt is possible for light to be reflected more than twice within a raindrop, and one can calculate where the higher order rainbows might be seen; but these are never seen in normal circumstances.
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It is a second rainbow caused by the way light reflects inside of raindrops.  They will appear between 50 and 53 degrees above the horizon and the colors are inverted.  There is also a band of darker sky between the two, this is called an Alexander's band.
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When we draw a circle with a compass, we keep the angle between the two legs constant.\n\nA ray from the top most point on the rainbow to our eye makes an angle to the horizontal direction. Theory says this angle is a constant.\n\nImagine the ray as one leg of long compass and the horizontal direction as another leg which points the center. Keeping the angle constant when the compass is rotated an arc is formed. \n\nIf we go high up we can see the whole circle.
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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.
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In Austria there are many rainbows, especially in summer when it rains a lot in the mountains. The most special was when I saw a double rainbow.
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Cause squares would look weird