Dispersion, Refraction and Internal reflection are all involved. | Phenomenon | Role in rainbow formation | |------------|---------------------------|
| Refraction | Sunlight bends when it enters the raindrop and again when it exits, changing direction at each air–water boundary. |
| Dispersion | Different wavelengths refract by slightly different angles, so the white light spreads into its constituent colours inside the drop. |
| Internal reflection | Part of the dispersed light reflects from the rear surface of the droplet and heads back toward the observer, making the coloured arc visible. | Thus, the combined effect of Refraction → Dispersion → Internal Reflection → Refraction in order produces the familiar rainbow spectrum.