A considerable part of the harmful UV rays of the sun does not reach the surface of the earth. This is because high above the earth's atmosphere, there is a layer of (a) \(\mathrm{CO}_{2}\) (b) \(\mathrm{O}_{3}\) (c) NO (d) \(\mathrm{SO}_{2}\)

The Earth is enveloped by a blanket of gases known as the atmosphere, which plays a critical role in sustaining life. Among these gases, some are particularly crucial for filtering out the sun's damaging ultraviolet (UV) rays before they reach the ground. The atmosphere acts as a natural sunscreen, with each layer performing its own distinct function.

In addition to providing oxygen for us to breathe, the atmospheric gases, which include nitrogen (N2), oxygen (O2), argon (Ar), carbon dioxide (CO2), and trace amounts of others like neon (Ne), perform the critical task of protecting life by absorbing and scattering solar radiation. Without this protective shield, living organisms would be exposed to intense UV radiation, which can cause skin cancer, cataracts, and other health problems, as well as damaging delicate ecosystems.

The ozone layer is a band of ozone (O3) molecules situated in the stratosphere, approximately 10 to 30 kilometers above the Earth's surface. This layer is our planet's primary defense against the sun's harmful ultraviolet B (UVB) rays.

The significance of the ozone layer lies in its ability to absorb approximately 97-99% of the sun's medium-frequency ultraviolet light, which could potentially harm the skin in the form of sunburns or more serious skin conditions. Furthermore, the ozone layer's protection extends to preserving aquatic ecosystems and agricultural productivity by filtering UV rays that could otherwise damage plant life and marine habitats. In recognition of its importance, international agreements such as the Montreal Protocol have been established to protect the ozone layer by banning or reducing the production of ozone-depleting chemicals such as chlorofluorocarbons (CFCs).

Ozone, known by the chemical formula O3, is a triatomic molecule, meaning it consists of three oxygen atoms. Unlike the diatomic oxygen (O2) that we breathe, ozone is less stable and far more reactive due to the presence of a third oxygen atom.

In the stratosphere, ozone is formed naturally when highly energetic UV light splits an oxygen molecule (O2) into two separate atoms. These free oxygen atoms can then collide with unbroken O2 molecules, creating ozone (O3). This illustration of the chemical nature of ozone explains its exceptional suitability in the role of UV filtration; its reactivity allows it to absorb the energy from UV radiation, breaking and reforming continually, which helps shield the Earth's surface from these potentially damaging rays.