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Rayleigh scattering (named after Lord Rayleigh) is the scattering of light by particles in the atmosphere; it is the reason why the sky is blue. |
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Rayleigh scattering (named after Lord Rayleigh) is the scattering of light by particles smaller than the wavelength of the light. It occurs when light travels in transparent solids and liquids, but is most prominantly seen in gases. Rayleigh scattering of sunlight from particles in the atmosphere is the reason why the sky is blue. |
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Rayleigh scattering of photons by Earth's atmosphere is dependant upon the size of the particles causing the scattering and the wavelength of the photon being scattered. This results in blue photons being scattered across the sky to a greater extent than photons of a longer wavelength, and so one sees blue light coming from all regions of the sky whereas the rest is still mainly coming directly from the Sun. |
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The amount of Rayleigh scattering that occurs to a beam of light is dependent upon the size of the particles and the wavelength of the light; in particular, the intensity of the scattered light is inversely proportional to the fourth power of the wavelength. This means that blue light is scattered much more than red light. In the atmosphere, this results in blue photons being scattered across the sky to a greater extent than photons of a longer wavelength, and so one sees blue light coming from all regions of the sky whereas the rest is still mainly coming directly from the Sun. |
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A notable exception is during sunrise? and sunset?, when the Sun's light must pass through a much greater thickness of the atmosphere to reach an observer on the ground. This extra distance allows the scattering of longer wavelengths to become more pronounced as well, resulting in red-hued skies. |
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A notable exception occurs during sunrise? and sunset?, when the Sun's light must pass through a much greater thickness of the atmosphere to reach an observer on the ground. This extra distance causes multiple scatterings of blue light, but relatively little scattering of red light; this is seen as a pronounced red-hued sky in the direction towards the sun. |
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