Artificial way of causing rainfall to reduce air pollution makes use of (UPSC Prelims 2025)

Question

The correct answer is [A] silver iodide and potassium iodide. The process of artificially inducing rain is known as Cloud Seeding, which is a weather modification technique used to manage water resources or mitigate air pollution.

Cloud Seeding Mechanism: This technique involves dispersing substances into the air that serve as cloud condensation nuclei or ice nuclei. These substances provide a surface for water vapor to condense or freeze upon, eventually becoming heavy enough to fall as precipitation.
Key Agents (Statement A - Correct): Silver iodide (AgI) is the most commonly used chemical because its crystalline structure is very similar to that of natural ice. Potassium iodide (KI) is also frequently used as an effective seeding agent. Other substances like dry ice (solid carbon dioxide) or simple table salt (sodium chloride) can also be used depending on the cloud temperature.
Pollution Mitigation: When it rains, a process called \"washout\" occurs. The falling raindrops collide with and capture suspended particulate matter (PM_{2.5} and PM_{10}) and absorb certain gaseous pollutants from the atmosphere, effectively \"cleansing\" the air and bringing the pollutants down to the ground.
Incorrect Options (B, C, and D): Silver nitrate (AgNO₃) and various forms of potassium nitrate or pure potassium are not standard agents for cloud seeding. Silver nitrate is highly soluble in water and lacks the specific crystal lattice structure required to mimic ice crystals effectively.

Historically, cities like Delhi have considered cloud seeding during peak winters to combat severe smog levels, though its success depends heavily on specific meteorological conditions like humidity and cloud cover.

GKToday Admin · Accepted Answer

silver iodide and potassium iodide The correct answer is [A] silver iodide and potassium iodide. The process of artificially inducing rain is known as Cloud Seeding, which is a weather modification technique used to manage water resources or mitigate air pollution.

Cloud Seeding Mechanism: This technique involves dispersing substances into the air that serve as cloud condensation nuclei or ice nuclei. These substances provide a surface for water vapor to condense or freeze upon, eventually becoming heavy enough to fall as precipitation.
Key Agents (Statement A - Correct): Silver iodide (AgI) is the most commonly used chemical because its crystalline structure is very similar to that of natural ice. Potassium iodide (KI) is also frequently used as an effective seeding agent. Other substances like dry ice (solid carbon dioxide) or simple table salt (sodium chloride) can also be used depending on the cloud temperature.
Pollution Mitigation: When it rains, a process called \"washout\" occurs. The falling raindrops collide with and capture suspended particulate matter (PM_{2.5} and PM_{10}) and absorb certain gaseous pollutants from the atmosphere, effectively \"cleansing\" the air and bringing the pollutants down to the ground.
Incorrect Options (B, C, and D): Silver nitrate (AgNO₃) and various forms of potassium nitrate or pure potassium are not standard agents for cloud seeding. Silver nitrate is highly soluble in water and lacks the specific crystal lattice structure required to mimic ice crystals effectively.

Historically, cities like Delhi have considered cloud seeding during peak winters to combat severe smog levels, though its success depends heavily on specific meteorological conditions like humidity and cloud cover.

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