Question

Question #762d1

Answer 1

This is due to a phenomenon called Scattering. Basically scattering is the effect of the interaction of light (from the Sun for example) with dust and molecules suspended into our atmosphere.
Radiation interacts with a particle and the particle re-radiate in all possible directions (possibly away from the original direction, such as our eyes).

The fact is that short wavelengths are scattered more (it is easier for them to Interact with the "small" particles in the atmosphere), basically according to the formula:

Scattering`prop1/lambda^4`
where `lambda` is the wavelength.
(for example, violet is scattered 10 times more than red light!!!)
(Ref: F. A. Jenkins, Fundamental of Optics)

In the morning (or late in the evening) when the Sun is low on the horizon, light rays has to pass through a longer path through the atmosphere, long enough to scatter and eliminate all short wavelengths (violet, blue, green...) leaving only red to reach our eyes!!!

Now you can see why at midday the Sun and the sky look....??? :-)

hope it helps