Why sky is blue?

As sunlight reaches the earth atmosphere, it encounters the gas molecules. These molecules which intercept the light have a tendency to absorb their specific region of the light spectrum (VIBGYOR). Mostly blue and violet which have low wavelength and high energy, which has wavelength approximately equal to that of oxygen atom diameter, gets absorbed in high quantity. These molecules then radiate these colors and scatter them across the sky. The reason why we perceive the sky as blue and not violet is because our eyes are more sensitive to blue. Thus sky looks blue.



When you look at horizon level, there is lot of distance. So the emitted light from the molecules gets reabsorbed by other molecules and hence sky looks a little pale blue in that direction.