Photochemical smog is formed due to presence of

Options

A. oxides of sulphur
B. oxides of nitrogen
C. winter during morning time.
D. winter during day time.

Explanation

**Step-by-Step Solution:**

1. **Understanding Photochemical Smog**: Photochemical smog is a type of air pollution that is formed when sunlight reacts with pollutants such as volatile organic compounds (VOCs) and nitrogen oxides (NOx) in the atmosphere.

2. **Key Components of Photochemical Smog**: The main components that contribute to the formation of photochemical smog include:
- Unsaturated hydrocarbons (VOCs)
- Nitrogen oxides (NOx)
- Ozone (O3)
- Peroxyacyl nitrate (PAN)

3. **Chemical Reactions Involved**:
- Unsaturated hydrocarbons and carbon compounds undergo oxidation, leading to the formation of aldehydes and ketones.
- These compounds then react with nitrogen dioxide (NO2) to form peroxyacyl nitrate (RCO3NO2).

4. **Conditions for Formation**: Photochemical smog typically forms in the presence of sunlight, as the energy from the sun (photons) is necessary to drive the chemical reactions that produce smog.

5. **Identification of Correct Answer**:
- The question asks for the presence of which components lead to the formation of photochemical smog.
- Based on the information, the presence of nitrogen oxides (NOx) is crucial for the formation of photochemical smog.

6. **Conclusion**: Therefore, photochemical smog is formed due to the presence of nitrogen oxides (NOx) and unsaturated hydrocarbons, making the correct answer option B (presence of nitrogen oxides).

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