Rainbow formation is due to combined effect of refraction, total internal reflection and dispersion.

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question states that rainbow formation is due to the combined effect of refraction, total internal reflection (TIR), and dispersion. We need to determine if this statement is true or false.

2. **Conditions for Rainbow Formation**: Rainbows typically form when sunlight interacts with raindrops in the atmosphere. This interaction involves three key processes: refraction, dispersion, and total internal reflection.

3. **Refraction**: When light enters a raindrop from air (a rarer medium to a denser medium), it bends. This bending of light is known as refraction. The amount of bending depends on the angle at which the light enters the droplet and the refractive index of the water.

4. **Dispersion**: As light refracts, it also disperses into its constituent colors (red, orange, yellow, green, blue, indigo, violet). This happens because different colors of light have different wavelengths and refract at slightly different angles.

5. **Total Internal Reflection**: After dispersion, the light reflects off the inside surface of the raindrop. For this reflection to occur, the angle of incidence must be greater than the critical angle for water. This is known as total internal reflection.

6. **Final Refraction**: After total internal reflection, the light exits the droplet. As it exits, it undergoes another refraction, which further separates the colors.

7. **Conclusion**: Since all three processes (refraction, dispersion, and total internal reflection) are necessary for the formation of a rainbow, we can conclude that the statement is true. The rainbow is indeed formed by the combined effect of these three phenomena.

### Final Answer:
The statement "Rainbow formation is due to the combined effect of refraction, total internal reflection, and dispersion" is **True**.

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