Photochemical smog:
Formed when sunlight acts on nitrogen oxides (NOx) and hydrocarbons (unburnt fuel), producing secondary pollutants like ozone
(O3​), peroxyacetyl nitrate (PAN), formaldehyde, etc.
It is also called Los Angeles smog or summer smog.
It mainly occurs in warm, dry, and sunny climates.
Option A:
It is controlled by the use of catalytic converters in automobiles.
Correct. Catalytic converters reduce emissions of NOx and hydrocarbons, which are precursors of photochemical smog.
Option B:
It causes corrosion of metals.
Correct. Ozone and other oxidants in photochemical smog can corrode metals.
Option C:
It is a mixture of
SO2​, smoke, and fog.
Not correct.
This describes classical smog (also called London smog or reducing smog), which occurs in cool, humid conditions and is a mixture of
SO2​ and particulates with fog.
Photochemical smog, on the other hand, contains NOx, hydrocarbons, and oxidants such as ozone-not SO2-based smoke and fog.
Option D:
It causes extensive damage to plant life.
Correct. Ozone and PAN damage leaves and affect photosynthesis.