Final answer:
Photochemical smog requires nitrogen oxides (NOx), volatile organic compounds (VOCs), and sunlight to form. These ingredients combine in a reaction facilitated by UV rays to create a harmful brown haze particularly over cities with warm, sunny climates.
Step-by-step explanation:
Requirements for Photochemical Smog Formation The formation of photochemical smog requires specific conditions. Here are three fundamental requirements: These three components combine, particularly in the presence of a warm, sunny climate, to form photochemical smog, characterized by a brown haze above cities. This type of smog is particularly harmful to human health, affecting the respiratory system and exacerbating conditions like asthma, bronchitis, and emphysema.