Changes

==Origin==

==Origin==

before [http://en.wikipedia.org/wiki/1000_AD 1000];  [https://nordan.daynal.org/wiki/index.php?title=English#ca._1100-1500_.09THE_MIDDLE_ENGLISH_PERIOD Middle English] reinbowe,  [https://nordan.daynal.org/wiki/index.php?title=English#ca._600-1100.09THE_OLD_ENGLISH.2C_OR_ANGLO-SAXON_PERIOD Old English] regnboga;  c. Old Norse regnbogi,  German Regenbogen

before [https://en.wikipedia.org/wiki/1000_AD 1000];  [https://nordan.daynal.org/wiki/index.php?title=English#ca._1100-1500_.09THE_MIDDLE_ENGLISH_PERIOD Middle English] reinbowe,  [https://nordan.daynal.org/wiki/index.php?title=English#ca._600-1100.09THE_OLD_ENGLISH.2C_OR_ANGLO-SAXON_PERIOD Old English] regnboga;  c. Old Norse regnbogi,  German Regenbogen

==Definitions==

==Definitions==

*1. a bow or arc of prismatic colors appearing in the heavens opposite the sun and caused by the refraction and reflection of the sun's rays in drops of rain. Compare primary rainbow, secondary rainbow.

*1. a bow or arc of prismatic colors appearing in the heavens opposite the sun and caused by the refraction and reflection of the sun's rays in drops of rain. Compare primary rainbow, secondary rainbow.

A rainbow spans a continuous spectrum of colours; the distinct bands are an artifact of human colour vision. The most commonly cited and remembered sequence, in English, is Newton's sevenfold red, orange, yellow, green, blue, indigo and violet (popularly memorized by mnemonics like Roy G. Biv). Rainbows can be caused by other forms of water than rain, including mist, spray, and dew.

A rainbow spans a continuous spectrum of colours; the distinct bands are an artifact of human colour vision. The most commonly cited and remembered sequence, in English, is Newton's sevenfold red, orange, yellow, green, blue, indigo and violet (popularly memorized by mnemonics like Roy G. Biv). Rainbows can be caused by other forms of water than rain, including mist, spray, and dew.

==Scientific Explanation==

==Scientific Explanation==

The [[light]] is first [[refracted]] entering 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 [http://en.wikipedia.org/wiki/Refractive_index refractive index]. Seawater has a higher refractive index than rain [[water]], so the [[radius]] of a "rainbow" in sea spray is smaller than a true rainbow. This is visible to the naked eye by a misalignment of these bows. The amount by which light is [[refracted]] depends upon its [http://en.wikipedia.org/wiki/Wavelength wavelength], and hence its [[colour]]. Blue light (shorter wavelength) is refracted at a greater angle than red light, but due to the reflection of light rays from the back of the droplet, the blue light emerges from the droplet at a smaller [[angle]] to the original incident white light [[ray]] than the red light. You may then think it is strange that the [[pattern]] of colours in a rainbow has red on the outside of the arc and blue on the inside. However, when we [[examine]] this issue more closely, we realise that if the red light from one droplet is seen by an [[observer]], then the blue light from that droplet will not be seen because it is on a different path from the red light: a path which is not incident with the observer's eyes. The blue light seen in this rainbow will therefore come from a different droplet, which must be below that whose red light can be observed.

The [[light]] is first [[refracted]] entering 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 [https://en.wikipedia.org/wiki/Refractive_index refractive index]. Seawater has a higher refractive index than rain [[water]], so the [[radius]] of a "rainbow" in sea spray is smaller than a true rainbow. This is visible to the naked eye by a misalignment of these bows. The amount by which light is [[refracted]] depends upon its [https://en.wikipedia.org/wiki/Wavelength wavelength], and hence its [[colour]]. Blue light (shorter wavelength) is refracted at a greater angle than red light, but due to the reflection of light rays from the back of the droplet, the blue light emerges from the droplet at a smaller [[angle]] to the original incident white light [[ray]] than the red light. You may then think it is strange that the [[pattern]] of colours in a rainbow has red on the outside of the arc and blue on the inside. However, when we [[examine]] this issue more closely, we realise that if the red light from one droplet is seen by an [[observer]], then the blue light from that droplet will not be seen because it is on a different path from the red light: a path which is not incident with the observer's eyes. The blue light seen in this rainbow will therefore come from a different droplet, which must be below that whose red light can be observed.

Contrary to popular [[belief]], the light at the back of the raindrop does not undergo [http://en.wikipedia.org/wiki/Total_internal_reflection 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.

Contrary to popular [[belief]], the light at the back of the raindrop does not undergo [https://en.wikipedia.org/wiki/Total_internal_reflection 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.

A rainbow does not [[actually]] exist at a particular location in the sky. Its 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]]. 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 [http://en.wikipedia.org/wiki/Antisolar_point 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 usually 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 above), on top of a [[mountain]], or above a waterfall.[http://en.wikipedia.org/wiki/Rainbow]

A rainbow does not [[actually]] exist at a particular location in the sky. Its 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]]. 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 [https://en.wikipedia.org/wiki/Antisolar_point 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 usually 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 above), on top of a [[mountain]], or above a waterfall.[https://en.wikipedia.org/wiki/Rainbow]

[[Category: General Reference]]

[[Category: General Reference]]