Why is the sky blue?
Why is the sky blue?
Ambrose Yim
Introduction
The sky’s blue tint seems like an eternal fact. There is a hidd when air is transparent?
en paradox: why should the sky be blue
Air (a mixture of 78% nitrogen, 21% oxygen and small quantities of other gases) is not transparent. Though the minuscule interactions between sunlight and air molecules are not immediately ap to us in daily life, trillions of air molecules multiply a phenomenon called backdrop to our lives. Scattering involves gaseous molecules absorbing light and reradiating it in all directions in the same colour. Each air m all frequencies of light in the visible spectrum are equally scattered and air molecules prefer to absorb blue light. In fact, it is the preferential scattering of blue light which lends white s traversing through the atmosphere a golden tinge. our sky. How do the energy-sucking bulbs impact the intensity of sunlight traveling through the atmosphere? It is found that the intensity of light Let be the intensity of a bundle of light passing throug cross-sectional area. It traverses a distance is proportional to the initial intensity and the distance traversed: scattering olecules is in effect a tiny solar powered bulb. However, not 198 Trillions of blue glowing light bulbs illuminate traversing the atmosphere decreases exponentially with distance. h a volume of scatterers with a constant . The fraction of light scattered out of th parent to form the blue unlight e path and lost
Where is a constant of proportionality called turbidity. Taking
to be infinitesimal,
199
Turbidity varies with different frequencies of light and scattering on the atomic scale to explain the preferential scattering of blue light in the atmosphere. we must look deeper into the mechanisms of
Interaction between light and atoms
The classical model of the atom is surprisingly helpful in understandin starting point for understanding many optical phenomena. small but massive positive nucleus surrounded by a symmetric light spherical cloud of electrons with g scattering and it serves as a 200 The classical atom is conceived as a
198 Falk, David S., Dieter R. Brill, and David G. Stork. ‘13.2 Rayleigh Scattering.’ Seeing the Light: Optics in Nature, Photography, Color, Vision, and Holography. New York: Harper & Ro 199 Meyer-Arendt, Jurgen R. ‘Chapter 16 Light Scattering.’ Introduction to Classical and Modern Optics. Englewood Cliffs, NJ: Prentice-Hall, 1995. 269 200 Lipson, S. G., and H. Lipson. ‘13 The Classical Theory of Dispersion. 1969. 469-503. Print. w, 1986. 347-349. Print. -83. Print. ’ Optical Physics. London: Cambridge U.P.,
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