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Where is the Ozone Layer?
| 1. Assumptions|
| 2. Introductory Material on Ozone|
| 3. Introductory Material on Photon Flux|
| 4. Establishing Basic Chemical Equations|
| 5. Formulation of a Differential Equation|
| 6. Graphical Analysis of I(a)|
| 7. Project Extension (optional)|
|     References|

Where is the Ozone Layer?
Part 1: Assumptions
1. We will use oxygen-only chemistry to estimate the ozone layer. Oxygen serves as both a creator and destroyer of ozone. While it is the only element that produces ozone, there are many other elements that destroy ozone. As a result, our model will overestimate the amount of ozone in the atmosphere. 2. We are using an altitude referencing system in which the earth's surface is defined as 0 km. We are also assuming that the path of the sunlight is perpendicular to the earth's surface. A fairly simple -- but interesting -- project extension allows you to examine the location of the ozone layer if the sunlight approaches through other angular paths. 3. We are using the Ideal Gas Law in this model, but air is not really an ``ideal'' gas. Ideal gases do not exist in nature, but the Ideal Gas Law is often a sufficiently close approximation to explain the behavior of many real gases. 4. Since oxygen, O2, is the only component of air that produces ozone (by photochemical and chemical reactions), our model will center on theO2 molecule. The O2 molecule consumes light energy to form ozone, so we will build a model for light intensity (photon flux) as a function of altitude by looking at how the presence of O2 affects incoming light intensity from the sun. 5. Although it is fairly obvious that temperature varies with altitude, for the purposes of this project we will assume that temperature remains constant. Specifically, we will assume that the air temperature is 285 degrees Kelvin, which is an estimate of the global average air temperature near the surface of the earth. Where is the Ozone Layer?

Part 2: Introductory Material on Ozone
The ozone layer has become a major topic of discussion among environmentalists, scientists and even the general public. Reports of holes in the ozone layer over Antarctica have raised considerable concern about environmental policy and have prompted many governments of the world to impose strict regulations regarding the release of ozone-depleting chemicals into the atmosphere. Located in the upper atmosphere, the ozone layer is a blanket of ozone gas, O3, which until recently completely enveloped the earth and its lower atmosphere. Ozone is a highly unstable compound formed as a result of photochemical dissociation of the normal oxygen molecule, O2, which is in abundance and comprises about 21% of the earth's atmosphere. Ozone, on the other hand, makes up a very small percentage of the atmosphere -- less than one part in 1026 of all the oxygen in the atmosphere is present as ozone [2, p. 125]. As a matter of fact, if one were to take all of the ozone in the atmosphere at OoC and compress it to a pressure of 1 atmosphere, the thickness of the ozone layer over the earth's surface would be 0.34 cm on average [2, p. 123]. Thus, the ozone layer is a very reactive envelope of gas consisting of the fairly scarce O3molecule. The importance of ozone rests in its ability to absorb ultraviolet (UV) radiation, the component of sunlight that is harmful to life. UV radiation is light of short wavelength, less than 400 nanometers (nm). Radiation of short wavelength has very high amounts of energy associated with it. For example, UV radiation has enough energy to break the bonds of certain organic molecules, particularly the genetic material, DNA [2, p. 121], present in living tissues such as skin. In some cases the products of these photolyzed organic molecules are reactive fragments of molecules that can lead to the formation of various types of skin cancers. Sunburn is also the unpleasant result of prolonged...
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