Which of the following phenomenon light forms a rainbow?

Options

A. Reflection of light
B. Refraction
C. Total internal reflection
D. Reflection as well as refraction

Answer

To determine which phenomenon of light forms a rainbow, we can analyze the process step by step:

### Step-by-Step Solution:

1. **Understanding the Formation of a Rainbow**:
A rainbow is formed when sunlight interacts with water droplets in the atmosphere. This interaction involves multiple optical phenomena.

2. **Refraction**:
When sunlight enters a water droplet, it slows down and bends due to a change in medium from air to water. This bending of light is called refraction. As the light refracts, it disperses into its constituent colors (red, orange, yellow, green, blue, indigo, violet) because different colors of light bend by different amounts.

3. **Internal Reflection**:
After refraction, the light travels inside the droplet and reaches the back surface of the droplet. Here, it undergoes total internal reflection. This means that the light reflects off the inner surface of the droplet instead of passing through it.

4. **Second Refraction**:
The internally reflected light then travels back towards the front of the droplet. As it exits the droplet, it refracts again. This second refraction further separates the colors, enhancing the visibility of the rainbow.

5. **Conclusion**:
The overall process of forming a rainbow involves both refraction (when light enters and exits the droplet) and reflection (the internal reflection inside the droplet). Thus, the correct answer is that a rainbow is formed by both reflection and refraction.

### Final Answer:
The phenomenon that forms a rainbow is **reflection as well as refraction**.

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