BITSAT 2018 Paper

The ozone layer, existing between 20 to 35km above the earth’s surface, shield the earth from the harmful U. V. radiations from the sun.
Depletion of ozone is caused by oxides of nitrogen
N2O + hv → NO + N (reactive nitric oxide)
NO + O3 → NO2+O2
O3 + hv → O2 + O
NO2 + O → NO + O2
2O3 + hv → 3O−2 (Net reaction)
The presence of oxides of nitrogen increase the decomposition of O3