Explain briefly the cause of ozone layer depletion.

Explanation

Ozone layer is very useful for life on the earth. Ozone layer does not allow harmful ultraviolet radiations coming from the sun to fall on the surface of earth. But the main ozone depleting compound is CFCs (chlorofluorocarbon compounds). Chlorofluorocarbon compounds are also known as freons. These are introduced into the atmosphere by air-conditioners, refrigerators,plastic foams etc. When chlorofluorocarbon compounds enter the upper atmosphere, they get broken down due to ultraviolet radiations emitted from the sun. This dissociation of CFCs depletes the ozone layer by giving free radicals.
`CF_2 Cl_2 overset(hv)to overset(*)CF_2 Cl + overset(*)Cl`
`CFCl_3 overset(hv)to overset(*)CFCl_2 + overset(*)Cl`
The reactive free radicals of chlorine atom destroy the ozone layer through these reactions.
`overset(*)Cl + O_3 to Cloverset(*)O + O_2`
`Cloverset(*)O + O to overset(*)Cl + O_2`
It has been found that one molecule of CFC.s can destroy one lakh `O_3` molecules in the stratosphere. This ozone depletion leads to a large hole in the ozone layer and the hole formed is known as ozone hole.