Rainbow Wallpaper

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A rainbow is a meteorological phenomenon that is caused by reflection refraction and dispersion of light in water droplets resulting in a spectrum of light appearing in the sky. It takes the form of a multicoloured arc. Rainbows caused by sunlight always appear in the section of sky directly opposite the sun.

Rainbows can be full circles. However the observer normally sees only an arc formed by illuminated droplets above the ground and centered on a line from the sun to the observer's eye.

In a primary rainbow the arc shows red on the outer part and violet on the inner side. This rainbow is caused by light being refracted when entering a droplet of water then reflected inside on the back of the droplet and refracted again when leaving it.

In a double rainbow a second arc is seen outside the primary arc and has the order of its colors reversed with red on the inner side of the arc. This is caused by the light being reflected twice on the inside of the droplet before exiting it.

Rainbows span a continuous spectrum of colours. Any distinct bands perceived are an artefact of human colour vision and no banding of any type is seen in a black-and-white photo of a rainbow only a smooth gradation of intensity to a maximum, then fading towards the other side. For colours seen by the human eye the most commonly cited and remembered sequence is Newton's sevenfold red orange yellow green blue indigo and violet remembered by the mnemonic Richard Of York Gave Battle In Vain.

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