Scattering of Sunlight

Scattering of Sunlight by Air Particles

The air molecules and other particles in the atmosphere such as clouds and ice crystals scatter the sunlight differently. The air molecules scatter the different colors of sunlight depending on their wavelength. Of the three colors with short wavelengths, violet is the most scattered. However, its quantity in sunlight is minimal in relation to blue. Thus, it is overshadowed by the blue color. Similarly, the green light is not as readily scattered as the blue color. The result is the dominance of the blue color from the sun explaining why the sky is observed as blue.

Scattering of Sunlight by Other Particles

Ice crystals and clouds also scatter sunlight. These particles are larger than air molecules so they scatter all the colors of the sunlight equally. People see clouds as white because they scatter all colors of the sun that appear as white. Other particles in the atmosphere are bigger than the air molecules, ice crystals, and clouds. They also scatter all the light from the sun, making humans see the white.

            The nature of the air particles in the atmosphere influences the color of the sky that people see. When air molecules are clear due to the absence of other particles, the color of the sky is seen as deep blue. The presence of other particles in the atmosphere makes the color change to a bluish-white due to the scattering of the white colored light.

Visibility and scattering of sunlight

Even though violet is the most strongly scattered color of sunlight, it is rarely visualized due to its minimal quantity and the poor sensitivity of the human eye. The cones of the eye have three color receptors including green, red, and blue. As such, they are able to visualize other colors that are within the red, yellow, and orange spectrum, which can be attested by the changes in the color of the sun during the day. When the sun is setting or rising, it appears yellow, red or orange. Since the eyes have some sensitivity to those colors, the sun is seen as such.

It is true that the scattering of sunlight affects visibility. The vision of an individual is reduced on a day when there are many particles in the atmosphere. However, visibility is a process that involves coordination between the brain and the eye. Thus, a clear day cannot guarantee seeing forever. The process of seeing an image involves the scattering and absorption of light from the sun and the ground. Sometimes on a clear day, the scattered light becomes so bright that theimage disappears. Proper coordination of the eye-brain system is the major determinant of visibility.  

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