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The Ozone Layer
Ozone, O can either be good or bad.
Troposphere is the lowest layer of the Earth's atmosphere, extending from the Earth's
surface up to about 7km (above the poles) and to about 20km (above the tropics). bad
because it is an air pollutant with harmful effects on the respiratory systems of animals.
Stratosphere is the is the second layer of the Earth's atmosphere, containing the `ozone
layer', about 10km to 50km above the Earth's surface. good because it protects living
organisms by preventing harmful UV light from reaching the Earth's surface.
UV radiation from the sun has wavelengths in the range 270-400nm. The ozone layer filters out the
shorter wavelengths, less than 320nm. These wavelengths would be very damaging to life on Earth.
The ozone converts the UV radiation into heat and so the ozone layer has a higher temperature than
other parts of the upper atmosphere.
The concentration of ozone is maintained in the ozone layer by:
O molecules absorb high energy UV radiation with a wavelength less than 240nm, forming atomic
The O atoms react with the O molecules to form ozone molecules O . This process generates heat.
The O molecules formed absorb UV (wavelengths between 240-310nm), converting O molecules
back into O molecules and O atoms.
The atomic oxygen produced immediately reacts with other O molecules to reform ozone.
The overall effect is to convert penetrating UV radiation into heat, without any net loss of ozone
Removal of Ozone-slow rate but human activities can change the rate.
When an oxygen atom and an ozone molecule combine, they form two O molecules