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How do refraction reflection and dispersion create a rainbow?
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A rainbow is an atmospheric phenomenon created through the interaction of sunlight with raindrops, involving three primary optical processes: refraction, dispersion, and reflection.
- Refraction: As sunlight enters a raindrop, it slows down and changes direction, bending as it passes from the air into the water.1
- Dispersion: Because white light is composed of various wavelengths, each color bends at a slightly different angle. This process, known as dispersion, separates the light into its component colors.12
- Reflection: Once inside the droplet, the light hits the back surface and undergoes internal reflection, bouncing back toward the front of the drop.1
- Final Exit: As the light exits the raindrop, it undergoes a second refraction, which further separates the colors and directs them toward the observer.1
The observer sees the most intense light at a specific angle of deviation, forming a circular arc of colors. While the primary bow results from a single internal reflection, a secondary, fainter bow with reversed colors can occur if light reflects twice within the droplets.1