What will be the colour of the sky as seen from the Earth if there were no atmosphere?

Why does the Sun look reddish at the time of sunrise and sunset?

Which of the following statements is true regarding rainbows?

In a given direction,the intensities of the scattered light by a scattering substance for two beams of light are in the ratio of $256:81$. The ratio of the frequency of the first beam to the frequency of the second beam is:

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?

The Sun is visible before actual sunrise and after actual sunset for some time. Explain this phenomenon.