Ultra Violet radiations from sunlight cause a reaction which produces

Ultra Violet radiations from sunlight cause a reaction that produces O₃.
Ozone is formed from dioxygen by the action of ultraviolet (UV) light and electrical discharges within the Earth's atmosphere.
It is present in very low concentrations throughout the latter, with its highest concentration high in the ozone layer of the stratosphere, which absorbs most of the Sun's ultraviolet (UV) radiation.