Why does the Sun have an elliptical shape at the time of sunrise and sunset? It is due to:

Why does the sky appear blue when we look at it?

Let $S_1$ be the amount of Rayleigh scattered light of wavelength $\lambda_1$ and $S_2$ that of light of wavelength $\lambda_2$ from a particle of size $a$. Which of the following statements is true?

Assertion : The setting sun appears to be red.
Reason : Scattering of light is directly proportional to the wavelength.

The sky would appear red instead of blue if

At sunrise or sunset,the sun looks more red than at midday because