Question

why is the Ozone layer of the atmosphere reffered as a protective shield

Answer 1

ozone layer is reffered as a protective shield because it blocks the harmful Ultraviolet
Ray's released from the sun which kills the organisms.ozone blocks the Rays and sends it back

Answer 2

Sun is the ultimate source of light and energy for earth.
Some rays are harmful for living organisms called ultraviolet ray . This ozone layer in atmosphere filter these ray and send back to space .
so it is called protective layer shield.