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 causes the formation of a rainbow, we can analyze the process step by step.

### Step-by-Step Solution:

1. **Understanding the Environment**:
- Rainbows are typically observed during or after rain when sunlight is present. The atmosphere contains numerous tiny water droplets suspended in the air.

2. **Incident Sunlight**:
- The sunlight, which is composed of different colors (red, orange, yellow, green, blue, indigo, violet), strikes these water droplets.

3. **Refraction of Light**:
- When the sunlight enters a water droplet, it slows down and bends due to refraction. This bending of light occurs because light travels at different speeds in different mediums (air and water).

4. **Dispersion of Light**:
- As the light refracts, it separates into its constituent colors. This process is known as dispersion. Each color bends at a slightly different angle, resulting in the formation of a spectrum.

5. **Total Internal Reflection**:
- After the light has been dispersed, it reflects off the inner surface of the droplet. This reflection is known as total internal reflection. It occurs when the angle of incidence is greater than the critical angle for the water-air interface.

6. **Exiting the Droplet**:
- The light then exits the droplet, undergoing another refraction as it moves from water back into air. This further separates the colors.

7. **Formation of the Rainbow**:
- The combined effect of refraction, dispersion, and reflection leads to the formation of a circular arc of colors in the sky, which we perceive as a rainbow.

### Conclusion:
The formation of a rainbow is caused by the combined phenomena of **refraction** and **total internal reflection** of light in water droplets.

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