Artificial way of causing rainfall to reduce air pollution makes use of
Answer & explanation
Answer: (a) silver iodide and potassium iodide
Artificial rain is made by cloud seeding: seed particles are added to a cloud so that rain can form, and Delhi has trialled it as an emergency measure against pollution episodes. India's IITM names silver iodide as the standard seeding agent for cold clouds, and UPSC's key pairs it with potassium iodide.
- ✓ (a) Both agents are iodides. IITM's CAIPEEX pages name silver iodide (AgI) as the ice-nucleating agent used in glaciogenic seeding; UPSC's key names potassium iodide as the second agent, which the IITM pages do not mention.
- ✗ (b) Silver nitrate replaces silver iodide here; the key's answer has both agents as iodides.
- ✗ (c) Potassium nitrate replaces potassium iodide here; the key's answer has both agents as iodides.
- ✗ (d) Silver nitrate and potassium chloride replace both iodides.
Remember · Cloud seeding uses iodide salts, chiefly silver iodide (with potassium iodide in the key), to trigger rain.
Sources
- Press Release: CAIPEEX, Scientific Cloud Seeding Experiment 2018, Indian Institute of Tropical Meteorology (Ministry of Earth Sciences) ↗ · reference work “A seeder and an instrumented research aircraft are being used to seed clouds and record the changes in clouds, leading to rainfall”
- Indian Institute of Tropical Meteorology (Ministry of Earth Sciences), CAIPEEX cloud seeding FAQ (Misc. Publication 2024) ↗ · reference work “Glacigenic seeding: In a cloud with a temperature below freezing (0oC), typically, silver iodide (AgI) is used as the seeding agent, and the seeding method is called glaciogenic seeding.”
- PIB (Ministry of Earth Sciences): Parliament question, Assessment of cloud seeding in Delhi, 5 February 2026 ↗ “At present, the cloud seeding activity is at trial stage with the objective to have one more option to provide relief as an emergency measure during episodic high air-pollution events when conducive cloud cover is present.”
Question and answer: UPSC's official GS Paper I (2025, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). ·