Rayleigh scattering is the scattering of light by particles or molecules that are much smaller than the wavelength of the light itself. In Earth’s atmosphere, this occurs primarily when sunlight interacts with nitrogen and oxygen molecules. Shorter wavelengths, such as blue and violet light, are scattered much more strongly than longer wavelengths such as red light, which is why the sky appears blue and sunsets appear red or orange.
In horticulture, Rayleigh scattering influences the quality and colour of natural daylight reaching plants, especially when the sun is low on the horizon or light passes through a long path of atmosphere. However, it has little effect on indoor grow lights because the distance between the light source and the plant is too short for significant atmospheric scattering to occur.
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