How is ozone formed from the oxygen present in the atmosphere?

(N/A) The upper stratosphere consists of a considerable amount of ozone $(O_{3})$,which protects us from the harmful ultraviolet $(UV)$ radiations coming from the sun.
These radiations can cause skin cancer in humans. Therefore,it is important to maintain the ozone shield.
In the stratosphere,when $UV$ radiations act on dioxygen $(O_{2})$ molecules,the $UV$ radiations split molecular oxygen into free oxygen $(O)$ atoms. These oxygen atoms then combine with molecular oxygen to form ozone.
$O_{2(g)} \stackrel{UV}{\longrightarrow} O_{(g)} + O_{(g)}$
$O_{(g)} + O_{2(g)} \stackrel{}{\longrightarrow} O_{3(g)}$
Ozone is thermodynamically unstable and decomposes back into molecular oxygen. Thus,a dynamic equilibrium exists between the production and decomposition of ozone molecules.