Question

How does it become possible to cause artificial rain by spraying silver iodide on the clouds?

Answer 1

As we know rainfall occurs when oppositely charged clouds meet, since, clouds are colloidal in nature and carry charge. Spray of silver iodide, an electrolyte, leads to artificial rain. Sometimes electrified sand is also used for this purpose.

Answer 2

Clouds are colloidal in nature and charge carriers . Spray of silver iodide, is an electrolyte, which results in coagulation, which is  leading to the artificial rain.