Why sun appears Red at evening & morning ?
vibgyor-placed according to higher to lower frequencies of colours emitted from the visible spectrum of sunlight rayleigh’s law states scattering is more for the higher frequency light waves since in the morning and evening the light waves travel a longer distance of atmosphere than a mid noon vertical light waves, short frequency blue waves are scattered more than the long frequency red waves so that only the sky appears red in the set and rise moreover our eyes are tuned for blue and red colours primarily, the other short and long frequency colours appears faintly
The photons that reach the earth from the sun are always the same and because they contain a mixture of all colors they represent pure white light. The photons must travel through the atmosphere to reach your eye and the length of the path is much shorter (through air) with the sun almost directly above than when it is on the horizon (sunrise or sunset). The different colors of the combined sunlight have different wavelengths and are scattered differently depending on the length of the path. You “see” the photons that have not been scattered. That is why the sky is blue on a sunny day at noon but red at sunrise and sunset. In fact at sunrise and sunset so much sunlight has been scattered that you can often look at the sun without protective glasses which is not possible at noon on a sunny day.
It is due to three factors: refraction of the light from the sun by the increased length of travel of the light through dense atmosphere when the sun is low on the horizon, scattering of the bluer components of the sunlight by the atmosphere, and the additional scattering of blue by particulates in the atmosphere. The last gave rise (unknowingly) to the old phrase “red sky at night, sailor’s delight, red sky at morning sailor’s take warning.” This particular phrase has truth to it: if the atmosphere is dusty at dusk it means areas to the west (normally the direction from which weather patterns travel, at least in the mid latitudes) are dry, hence dust is blown up by the wind. In the morning, if it is red, it means the wind has persisted and weather patterns may be changing. Of course this does not always work.
