Dear Student,
The Ozone layer in the atmosphere protects the earth's surface from the harmful UV radiations from the Sun. The ozone layer protects the Earth acting as a barrier which absorbs and reflects most of the UV rays.
The meteorites if hit on Earth can be dangerous depending upon their size and location of impact. But most of the meteorites that enter the Earth's atmosphere will be reduced to smaller size and will burn up before reaching the Earth's surface.
Regards