• # question_answer 50)   From where does ozone come in the photochemical smog?

Sunlight causes photochemical decomposition of $N{{O}_{2}}$ into NO and O. $N{{O}_{2}}+hv\to NO+O$ Atomic oxygen is a highly reactive species. It combines with diatomic oxygen and forms ozone. ${{O}_{2}}+O+M\to {{O}_{3}}+M$ Where M is inert gas such as nitrogen. Thus, ${{O}_{3}}$ is formed during the formation of smog.