Question

how ozone layer is formed

Answer 1

O2 is spilitting into O
and one O is combine with O2
to form O3
O+O2= O3

Answer 2

ozone layer at the higher level of the atmosphere is a product of UV radition acting on oxygen (O2) molecule. The higher energy UV radition splits. A part some molecule of oxygen (o2) reacts with few molecule of oxygen (o) atoms then these combine to form ozone