Question

Photochemical smog was first observed in:

• A. London
• B. Tokyo
• C. Los Angeles
• D. Paris

Answer 1

Answer: (C)

Photochemical smog was first observed in Los Angeles in the 1940s.

A photochemical smog is the chemical reaction of sunlight, nitrogen oxides $\left(N{O}_x\right)$ and volatile organic compounds $\left(VOCs\right)$ in the atmosphere, which leaves airborne particles (called particulate matter) and ground-level ozone.

Option B is correct.