| Ozone Layer |
| Ozone is formed from automobile emissions and is an urban air pollutant, but it is also formed naturally in the stratosphere. At altitudes of 20 to 30 kilometers, high-energy ultraviolet (UV) radiation breaks diatomic oxygen down to atomic oxygen, which then reacts with additional O2 to form ozone:
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This synthesis of ozone is of great benefit to life on the Earth because if the ultraviolet radiation absorbed in the reaction were to reach the Earth’s surface, it would cause immediate harm to living tissue. |
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When it absorbs ultraviolet radiation, ozone fragments into molecular oxygen and atomic oxygen. These molecules eventually re-form ozone. Because chemical bonds are created when ozone re-forms, heat energy is released:
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Thus harmful ultraviolet radiation is transformed by ozone into a not-so harmful slight heating of the stratosphere. Note that ozone is not lost in this transformation, which means it can continue to shield the Earth’s surface indefinitely from ultraviolet radiation.
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The concentration of ozone in the stratosphere is quite small. This ozone layer absorbs more than 95 percent of the ultraviolet radiation that comes to our planet from the sun. It is the safety blanket of Planet Earth.
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