The ozone layer that is inside the stratosphere blocks UV radiation.
The ozone layer contains high concentrations of ozone relative to other parts of the atmosphere. This was discovered by Charles Fabry and Henri Buisson who are both French Physicists.
The ozone in the earth's stratosphere is created through ultraviolet light striking a group of ordinary oxygen molecules containing two oxygen atoms, subsequently splitting them into individual oxygen atoms and finally these said atomic oxygen then combines with unbroken O2 to create ozone (O3).
The atmosphere of Earth is composed of 21% of Oxygen. Ultraviolet radiation is absorbed by the ozone layer which is present inside the stratosphere. Actually, the UV-radiation is used to break the oxygen molecule. The free oxygen atom then joins with another oxygen molecule and forms ozone (O₃). The ozone-oxygen cycle converts harmful UV -radiation into heat.