Why is sky blue ?

The sky appears blue because of the way sunlight interacts with the Earth's atmosphere. When sunlight reaches the Earth's atmosphere, it is scattered in all directions by the gases and particles in the air. Blue light is scattered more than other colors because it travels as shorter, smaller waves. This is why we see the sky as blue during the day.

The sky appears blue because of a phenomenon called Rayleigh scattering. When sunlight enters the Earth's atmosphere, it interacts with molecules of nitrogen and oxygen, which are much smaller than the wavelength of light. These molecules scatter the light in all directions, but they scatter blue light more effectively than other colors because blue light has a shorter wavelength. This is because the scattering of light depends on the wavelength of the light, and shorter wavelengths are scattered more effectively than longer wavelengths.

As a result, more blue light is scattered towards our eyes, and the sky appears blue during the day. At sunrise and sunset, the sunlight has to travel through more of the atmosphere to reach our eyes, and the blue light is scattered away more effectively, leaving the longer wavelengths of light, such as red and orange, to reach our eyes. This is why the sky appears red or orange at sunrise and sunset.