The Physics Factbook™
Edited by Glenn Elert -- Written by his students
An educational, Fair Use website
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|Boyd, Robert & Robert Morrison. Organic Chemistry. New Jersey, Prentice Hall, 1992: 70.||"This ozone layer is extremely diffuse, extending from an altitude of about 90 km down to about 30 km."||60 km|
|Stoker, Stephen. "Ozone." World Book. Chicago: World Book, 1993: 902.||"The highest concentration of ozone is reached between 9 and 8 miles (15 and 30 km) about earth's surface."||15 km|
|"Upper atmosphere Research Satellite: A Program to Study Global Ozone Change."NASA, 1989.||"Contrary to de Bort's early conclusion, the stratosphere is warmer than the upper troposphere: temperatures above the troposphere increases slowly with height up to about 50 M. However, an explanation for this phenomenon was not found until 1930, when a plausible theory was put forth by Sidney Chapman for the existence of a stratospheric ozone layer. Absorption of solar ultraviolet energy by ozone produces most of the heating in the middle atmosphere."||50 km|
|Horowitz, Irving, Contemporary Earth Science, New York: Amsco, 1976.||"The ozonosphere is located between about 6 and 35 miles (9.6 and 56 km) above sea level, and contains many ozone (O3) molecules."||46.4 km|
|Introduction to the Ozone Layer. Ozone Depletion FAQ. Utrecht University.||"If the ozone layer over the US were compressed to zero degrees Celsius and one atmosphere pressure, it would be about 3 mm thick. So 0.01 mm thickness at 0 °C and 1 ATM is defined to be 1 DU; this makes the average thickness of the ozone layer over the US come out to be about 300 DU"||3 mm
The ozone layer comprises the greater part of the stratosphere between altitudes of 10 and 50 km. The highest concentration of ozone is reached between 15 and 30 km. The concentration of ozone molecules is 10 parts ozone per 1 million parts air. Ozone, which is a form of oxygen, forms naturally from the dissociation (splitting) of oxygen molecules by ultraviolet radiation. One free oxygen atom (O) combines with an ordinary oxygen molecule (O2) to form ozone (O3).
The average thickness of the ozone layer is about 50 km but if compressed by sea-level pressures, it would be only a few centimeters thick. The Dobson Unit (DU) is a scale for measuring the total amount of ozone occupying a column of air. One DU is defined as 0.01 mm thickness at zero degrees Celsius and one atmosphere. If the ozone layer over the US were subjected to 0 °C and 1 atmosphere it would end up being 3 mm thick or 300 DU.
The ozone layer functions to protect the earth from harmful radiation that is emitted by the sun. It is thinning due to the release of man-made compounds called chlorofluorocarbons (CFC). The net effect that CFCs have on the ozone layer is to recombine an oxygen atom with an ozone molecule to form two oxygen molecules. From 1978 to 1991, global stratospheric ozone levels have decreased by 3%. In addition, the rate of ozone depletion increases with increasing latitude. As a result the US, Europe, and Australia have experienced a 4% decrease in ozone concentration.
Cho Cho Tan -- 2000
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