Artifical rain is caused by spraying :

Options

A. opposite charged collidal dust over a cloud
B. same charged collidal dust over a cloud
C. both
D. none of these

Answer

To solve the question regarding the cause of artificial rain, we can break down the explanation into clear steps:

### Step-by-Step Solution:

1. **Understanding Artificial Rain**:
- Artificial rain, also known as cloud seeding, is a process used to enhance precipitation from clouds.

2. **Role of Colloidal Dust**:
- In this process, colloidal dust particles are introduced into the atmosphere. These particles can carry a charge, which is crucial for the process to work effectively.

3. **Charged Particles in Clouds**:
- Clouds consist of tiny water droplets that can also carry charges. These charges can be positive or negative.

4. **Spraying Opposite Charged Dust**:
- When positively charged colloidal dust is sprayed into the clouds, it interacts with the negatively charged water droplets in the cloud. This interaction is essential for the process.

5. **Neutralization of Charges**:
- The positively charged dust neutralizes the negative charges on the water droplets. This neutralization causes the droplets to lose their repulsion towards each other.

6. **Coagulation of Water Droplets**:
- As the repulsion decreases, the water droplets can come closer together, coalesce, and grow larger.

7. **Formation of Larger Droplets**:
- Eventually, these larger droplets become heavy enough to fall as precipitation, resulting in artificial rain.

8. **Conclusion**:
- Therefore, the correct answer to the question is that artificial rain is caused by spraying opposite charged colloidal dust over a cloud.

### Final Answer:
The correct option is **A: opposite charged colloidal dust over a cloud**.

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