How ozone is formed?

Ozone layer covers the earth like a blanket, protecting it from the harmful ultraviolet rays of the sun. It is formed in two steps ,

i. Step 1: Photolysis or Photo dissociation.

The oxygen molecule, containing two O atoms, gets broken down or dissociated in the presence of ultraviolet light to give two free O atoms.

ii. Step 2: Fusion of atoms.

The free oxygen atoms, combine with the oxygen molecules to form ozone, containing three atoms of oxygen in one molecule.