Question

Biological importance of ozone layer is:
A) It stops ultraviolet rays.
B) Ozone layer reduces greenhouse effect.
C) Ozone layer reflects radio waves.
D) Ozone layer controls ${O_2}/{H_2}$ ratio in atmosphere.

Answer 1

Hint: Ozone layer is called earth’s protective umbrella as it stops the harmful ultraviolet rays that can cause skin cancer and other harmful skin problems.

Complete answer:
Ozone is a protective layer formed above the stratosphere. It is a light bluish gas-like substance that came into existence when plants release oxygen during photosynthesis which got accumulated in the stratosphere and reacted with the ultraviolet rays from the sun.
${O_2}\xrightarrow{{hv}}O + O$
The heat produced from UV rays splits the dioxygen to two oxygen atoms with sufficient energy. Further the oxygen atoms react with remaining dioxygen to form ozone.
$O + {O_2} \to {O_3}$ (Ozone)
Hence the ozone absorbs UV rays and prevents it from entering the earth’s atmosphere. Greenhouse effect occurs in the troposphere, the layer below the stratosphere due to carbon dioxide and sunlight it is the dust particles that reflect the sunlight back causing reduced greenhouse effect.

Hence the correct option is option (A).

Note: Due to the increasing use of air conditioners, refrigerators and aerosols ozone layer is depleting as the NO nitrogen oxide thus produced reacts with ozone resulting in its depletion. Such activity needs to be controlled or it could have adverse effects on man, animals and climate. The Stratosphere is called a warm layer as formation of ozone releases a lot of heat thus increasing the temperature.