If
you look at the sunset, you will find that it is usually red, with the colours
spreading across the sky. Sometimes on a hot day you may notice that the sun is
red too. Do you know why the sun or the sunset is red?
Of
course the sun has not suddenly changed colour. It only has that colour during
a certain time of the day. In fact, people looking at the sun thousands
kilometers to the west may not find it red at all! The colours of the sun are
produced by the distance that the sunlight has to travel throught the
atmosphere. The lower the sun is in the sky, the longer the distance the light
has to travel throught.
You
see sunlight is a mixture of light of all colours. This mixture of light usully
appears as white to our eyes. However, the atmosphere contains molecules of air,
dust, water vapor and other impurities. As the light passes throught them,
different colours are scattered by these particles. It happens that the
atmospherescatters violet, blue, and green light more than it scatters the red
or the yellow lights. When the sun is low in the sky, as during sunset, most of
the violet, blue and green lights are scattered. This leaves only red and yellow lights which spread across the
sky at sunset. That is why we have red sunset.
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