The electromagnetic radiation emitted by the sun. The total range of wavelengths of light emitted by the sun (99.9% in the range from \(150\ \text{to}\ 4000\ \text{nm}\)) is filtered on entering the earth's atmosphere, largely through the absorption by oxygen, ozone, water vapour and carbon dioxide. Near sea level only light of wavelengths longer than about \(290\ \text{nm}\) is present. The light from \(290{-}400\ \text{nm}\) is effective in inducing important photochemical processes since absorption by the important trace gases, ozone, nitrogen dioxide, @A00208@, @K03386@, etc., is significant in this region.