Step 1: Evaluating statements about ozone:
(a) Ozone is a poisonous gas.
This statement is true. Ozone (O₃) is toxic; high concentrations can be detrimental to humans and animals, causing respiratory issues and irritation to eyes and throat.
(b) Ozone shields the earth's surface from the infrared radiation from the sun.
This statement is false. Ozone primarily protects Earth from solar ultraviolet (UV) radiation, not infrared (IR) radiation. The ozone layer absorbs harmful UV rays, preventing skin cancer and cataracts.
(c) Ozone is a product of UV radiations acting on oxygen molecules.
This statement is true. UV radiation from the Sun dissociates oxygen molecules (O₂) into oxygen atoms (O). These atoms then combine with other O₂ molecules to form ozone (O₃) in the ozone-oxygen cycle.
(d) At the lower level of the Earth's atmosphere, ozone performs most essential functions.
This statement is false. While tropospheric ozone contributes to air pollution, its crucial functions occur in the stratosphere, where it forms a protective layer against harmful UV radiation.
Step 2: Conclusion:
The accurate statements are:
- (a) Ozone is a poisonous gas.
- (c) Ozone is a product of UV radiations acting on oxygen molecules.