Why does the red color appear at the horizon during sunset?
Asked by: Huma Naqvi
The red colour in the sky at sunset (and sunrise) is due to an effect called Rayleigh
scattering. There is a similar form of scattering called Mie scattering which is
responsible for the white colour of clouds.
Particles in our atmosphere that are approximately the same size as the wavelength of
visible light cause the white light from the sun to scatter and split into individual
components. Oxygen and Nitrogen (the main components of our atmosphere) scatter violet and
blue light due to their small size. This is why the sky appears to be blue in the day time,
especially at midday when the Sun is closest to us.
During sunrise and sunset the distance that the light has to travel from the Sun to an
observer is at its greatest. This means the a large amount of blue and violet light has
been scattered so the light that is recieved by an observer is mostly of a longer
wavelength and therefore appears to be red.