Photochemical smog is a resultant of the reaction among
Smart Elimination
The name 'Photochemical' implies Light (Photo) + Sun. So 'Presence of Sunlight' is mandatory. This eliminates C and D.
If you read the question carefully it says that photochemical smog is caused by a reaction, which means it is a secondary pollutant. Now for this to occur, there should be an intermixing of primary pollutants (NOx and Hydrocarbons) with sunlight.
Hence eliminate the options which do not contain NOx and sunlight.
Potential Trap
Confusing Classical Smog (London Smog - SO2, cool) with Photochemical Smog (Los Angeles Smog - NOx, Sunlight).
Answer Key & Explanation
Answer: AThe correct answer is Option A.
Explanation:
- Photochemical Smog: Also known as 'Summer Smog' or 'Los Angeles Smog'.
- Formation: It occurs in warm, dry, and sunny climates.
- Reactants: Nitrogen Oxides ($NO_x$) and Volatile Organic Compounds (VOCs) / Hydrocarbons.
- Process: Sunlight reacts with these pollutants to form secondary pollutants like Ozone ($O_3$) and Peroxyacetyl Nitrate (PAN).
- Result: Brown haze, eye irritation.
Option A correctly lists $NO_2$, $O_3$, and PAN in the presence of sunlight.
Value Addition
- Classical Smog: Smoke + Fog + $SO_2$. Occurs in cool, humid climates (London type). Reducing in nature.
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Foundational question based on core concepts.