Problem 46 - A Complete Resource Book in Chemistry for JEE Main

Question

Artificial rain is caused by spraying (a) neutral charged colloidal dust over a cloud (b) same charged colloidal dust over a cloud (c) both (a) and (b) (d) opposite charged colloidal dust over a cloud

Step-by-Step Solution

Answer

(d) Opposite charged colloidal dust over a cloud.

Step 1: Understanding Colloidal Dust Charged Type

Artificial rain is typically induced when charged particles are used to encourage cloud droplets to coalesce into larger droplets that eventually fall as rain. The charge of the colloidal dust used is crucial in determining the effectiveness of this process.

Step 2: Analyzing the Impact of Charge on Coalescence

In order for droplets to effectively combine and grow into raindrops, they must be able to overcome the repulsive forces that normally prevent them from coming together. Using opposite charges for the colloidal dust and the cloud particles enhances the coalescence because opposite charges naturally attract each other.

Step 3: Determining the Correct Option

From the options provided, the choice that would most likely lead to successful artificial rain is to use opposite charged colloidal dust. This is because opposite charges attract, increasing the likelihood of cloud particles coalescing into droplets large enough to fall as rain.

Key Concepts

Colloidal Dust

Colloidal dust plays a significant role in artificial rainmaking. These tiny particles are suspended in the air and can be charged to enhance their effect. This dust typically consists of substances like salt or silver iodide, which are capable of attracting water droplets.

• When sprayed into clouds, colloidal dust serves as nuclei for droplet formation.
• Different charges on the particles can affect how they interact with cloud droplets.

Using charged colloidal dust helps initiate the coalescence of small droplets. This process ultimately leads to increased droplet size, making precipitation more likely.

Cloud Coalescence

Cloud coalescence is crucial in the formation of raindrops. It involves the merging of smaller water droplets to form larger ones. For artificial rain to be effective, promoting coalescence is key.

• Droplets in clouds often exist as tiny particles suspended in the air.
• Coalescence occurs when these small droplets collide and stick together.

By using charged particles such as colloidal dust, the coalescence process is facilitated. This is because opposite charges between particles and droplets encourage them to join together more easily.

Induced Precipitation

Induced precipitation is essentially the process of making rain artificially. This is often achieved through methods like cloud seeding. The goal is to create conditions that favor rain formation, especially in dry areas.

• Induced precipitation uses technology and science to control rain occurrence.
• Cloud seeding is a popular method where substances are introduced into clouds to induce rain.

This method has been beneficial in enhancing agricultural productivity and water availability in arid regions. By carefully choosing the charged particles, the likelihood of inducing precipitation can be increased.

Charged Particles

Charged particles are integral to the process of creating artificial rain. These particles can be positively or negatively charged. The charge influences how they interact with other droplets in clouds.

• Opposite charges attract, while the same charges repel each other.
• In the context of artificial rain, opposite charged particles are more effective.

By using opposite charged particles, the particles and cloud droplets are more attracted to each other. This attraction increases the coalescence and growth of raindrops, leading to successful artificial rain formation.