Why do we see a rainbow in the sky only after rainfall?

Explanation

### Step-by-Step Solution:

1. **Understanding the Conditions for a Rainbow**: A rainbow is typically seen when there are water droplets in the atmosphere. This usually occurs after rainfall when the air is filled with tiny water droplets.

2. **Role of Water Droplets**: These suspended water droplets act like prisms. A prism is an optical element that can bend and disperse light into its constituent colors.

3. **Dispersion of Light**: When sunlight, which is composed of white light, enters a water droplet, it slows down and bends (refracts) at the surface of the droplet. This bending causes the light to split into its different colors (red, orange, yellow, green, blue, indigo, violet) due to the different wavelengths of light bending by different amounts.

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