Scattering of Light
As sunlight travels through the Earth’s atmosphere, it gets scattered by a large number of molecules present in the atmosphere.
According to Rayleigh
where Is = intensity of light scattered
λ = wavelength
Also, rays don’t undergo any change in wavelength on scattering.
Application of Scattering of light:
Blue Color of Sky:
As blue has the shorter wavelength than red, therefore; blue color is scattered much more.
White Color of Clouds:
Clouds contain very large particles such as water droplets, ice particles, dust particles etc. As x >> λ.
So, all colors are scattered in equal amount to give white color. Hence clouds appear white.
Sun looks reddish at the time of sunrise & sunset:
At the time of sunrise & sunset, the sun is near the horizon. The rays from the sun have to travel a large part of the atmosphere. As λblue < λred.
Therefore must of the blue light get scattered away & only red light enters our eyes.
Danger signals are red:
Because λred is large and thus is scattered least and can be seen from the maximum distance. That’s why danger signals are red.