| > s sending you more blue light than the background level. The background level is black! No air, no scattering.
d
> A cloud that isn't between you and the sun is getting its light from the sky background, which is blue. Why is the cloud not blue? The cloud is bathed in intense, direct sunlight which is slightly yellow, and it is exposed to a small amount of scattered blue light. It could be that this mixture whitens the color, essentially reconstituting the light. Why does white paint look pure white? Or snow on the ground? Same reason. It's reflecting the sky blue in a small amount, plus the yellowish sunlight. If you are in a dark enclosure like a cave or barn, and sunlight is streaming in through a small aperture, if you hold some white object up to that light, it doesn't look the same as if you do that outside because it's not illuminated by the blue sky, only by direct sunlight. Moreover, the shadowed parts white object sitting outdors, exposed to sunlight. tend to be tinged with blue. |
By "the background level", what I mean is the emission spectrum of the sun.
(And by "more blue", I mean in a relative sense, not an absolute sense.)