Dispersion explains the formation of a rainbow through the separation of sunlight into its component colors by water droplets in the atmosphere. Here’s how the process works:
- Refraction (Entry into the Droplet):
When sunlight enters a raindrop, it slows down and bends because water is denser than air. This bending is called refraction. Since different wavelengths of light bend by different amounts, white sunlight starts to split into colors — this is dispersion. - Internal Reflection:
Inside the droplet, the light reflects off the inner surface. During this reflection, the different colors remain separated due to their different paths. - Refraction (Exit from the Droplet):
As the light exits the droplet, it bends again. This second refraction causes the colors to spread out more clearly. - Color Separation:
Because each color bends at a slightly different angle, they emerge from the droplet at different directions. Red light typically exits at a higher angle (~42°), and violet at a lower angle (~40°). - Observer’s Perspective:
An observer sees different colors coming from different droplets at specific angles. Together, millions of droplets contribute to forming a circular arc of colors — the rainbow.
Thus, dispersion in water droplets is the key to splitting sunlight into the spectrum of colors that we see in a natural rainbow.