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Why is the sky blue and sunsets are red?
VallieValVal - 2009-04-01 01:47:24 - Physics
Why is the sky blue during the day and why the sunsets look red?
Best Answer:
THE REASON THE SKY IS BLUE: The blue color of the sky is due to Rayleigh scattering. As light moves through the atmosphere, most of the longer wavelengths pass straight through. Little of the red, orange and yellow light is affected by the air. However, much of the shorter wavelength light is absorbed by the gas molecules. The absorbed blue light is then radiated in different directions. It gets scattered all around the sky. Whichever direction you look, some of this scattered blue light reaches you. Since you see the blue light from everywhere overhead, the sky looks blue. THE REASON WHY SUNSETS ARE RED: Sunset colors are a result of scattering of sunlight by air molecules and small particles in the atmosphere. The scattering is wavelength-dependent; shorter wavelengths (violet and blue) are scattered out of the sun beam more strongly than are longer wavelengths (orange and red). This wavelength dependence produces two complementary effects: One, the scattered light from a clear sky is blue; and two, when the sun is low in the sky, so that the path through the atmosphere is long, the loss of blue light due to scattering leaves the remaining light orange or red. Clouds and other wavelength-independent (white) scatterers light up orange or red when illuminated by this light. A complete description of the light scattering in the atmosphere is given by Mie theory or the discrete dipole approximation.
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