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Atmospheric light scattering: Difference between revisions
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→Mie scattering on thin clouds
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At daytime, this creates a whiteout of a cloud when the sun is right behind it. If other, more dense clouds are also in the scene, this creates an impressive play of light and shadow: | At daytime, this creates a whiteout of a cloud when the sun is right behind it. If other, more dense clouds are also in the scene, this creates an impressive play of light and shadow: | ||
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[[File:Cloud_mie03.jpg|600px|Mie scattering during the day]] | [[File:Cloud_mie03.jpg|600px|Mie scattering during the day]] | ||
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Interestingly enough, cloud dominated by Mie scattering appear a relatively dark grey (as if they were in shadow) when seen from the side, even when they are fully illuminated. This is caused by the low probability of light scattered to large angles - since all light is focused forward, the side of the cloud becomes dark. | Interestingly enough, cloud dominated by Mie scattering appear a relatively dark grey (as if they were in shadow) when seen from the side, even when they are fully illuminated. This is caused by the low probability of light scattered to large angles - since all light is focused forward, the side of the cloud becomes dark. | ||
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At sunrise and sunset, the effect of Mie scattering is even more prominent - since the direct sunlight coming through the upper atmosphere is red-golden due to the effect of Rayleigh scattering, the Mie-halo created by light scattering in the clouds is also coloured. Combined with diffuse shading on denser clouds, this generates very vivid colors which change quickly as the sun rises higher and both light intensity and hue change. | At sunrise and sunset, the effect of Mie scattering is even more prominent - since the direct sunlight coming through the upper atmosphere is red-golden due to the effect of Rayleigh scattering, the Mie-halo created by light scattering in the clouds is also coloured. Combined with diffuse shading on denser clouds, this generates very vivid colors which change quickly as the sun rises higher and both light intensity and hue change. | ||
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[[File:Cloud_mie01.jpg|400px|Mie scattering on thin clouds during sunrise]] | [[File:Cloud_mie01.jpg|400px|Mie scattering on thin clouds during sunrise]] | ||
[[File:Cloud_mie02.jpg|400px|Mie scattering on thin clouds during sunrise, a bit later]] | [[File:Cloud_mie02.jpg|400px|Mie scattering on thin clouds during sunrise, a bit later]] | ||
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Mie scattering is essentially absent whenever a cloud becomes opaque, i.e. when it is larger than the light attenuation length in the cloud. | Mie scattering is essentially absent whenever a cloud becomes opaque, i.e. when it is larger than the light attenuation length in the cloud. | ||