Why rainbow is in an arc shape?

Answer 1

A rainbow is actually round. On the ground, the bottom part is hidden, but in the sky, like from the view of a flying airplane, it can be seen as a round shape.

Answer 2

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 aeroplane, 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.

Answer 3

he 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 aeroplane, 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.

Answer 4

When we see rainbows we see them as arcs when in truth they are formed as circles. There is a point called the antisolar point that the rainbow seems to form around. From the picture we see the antisolar point formed as a line from the observers head by the sun shining from behind.
--We don't see the full circle of the rainbow because the horizon gets in the way. As the sun goes down we are able to see more of the rainbow, and the higher the sun is in the sky the smaller the arc seems.
--Sometimes people at high elevations, like in planes, see rainbows as full circles because they do not have the horizon to block their view.

Answer 5

as quickly as we see rainbows we see them as arcs whilst in reality they are shaped as circles. there's a element called the antisolar element that the rainbow looks to style around. we don't see the completed circle of the rainbow because of the fact the horizon gets in the way. because of the fact the solar is going down we are waiting to confirm greater of the rainbow, and the better the solar is in the sky the smaller the arc looks. each each now and then human beings at intense elevations, like in planes, see rainbows as finished circles because of the fact they don't have the horizon to block their view.

Answer 6

b/c when it's formed, dropplets of water in the air act as prisms for the sunlight. it's in an arc b/c the world is in a sphere, causing the atmosphere to curve. therefore, a rainbow curves.

Answer 7

That follows the arc of the earth.

Answer 8

its a reflection from the suns rays

Answer 9

bends with the surface of the planet...