How Do Rainbows Form: The Science Behind the Spectacle
A rainbow forms when sunlight meets water droplets in the atmosphere. This process involves the reflection, refraction, and dispersion of light. Here’s how it happens:
- Sunlight enters a water droplet, slowing down and bending as it moves from air into water (refraction).
- The amount of bending is determined by the color of the light, with shorter wavelengths (blue and violet) bending more than longer wavelengths (red and orange), thus spreading out the light into its individual colors (dispersion).
- The refracted light then reflects inside the water droplet. During this reflection, the light stays within the droplet.
- The light exits the droplet, bending again as it moves from the water back into the air (secondary refraction), further separating the colors.
- These combined processes create a circular arc of colors, usually with red on the outside and violet on the inside.
- For an observer on the ground, the angle at which the light exits the droplets and reaches the observer’s eyes is about 42 degrees from the direction opposite the sun, determining the position and appearance of the rainbow.
In summary, a rainbow is formed through the refraction, dispersion, and internal reflection of sunlight in water droplets, separating light into its constituent colors and creating the circular arc we see.
Read more…
https://www.metoffice.gov.uk/weather/learn-about/weather/optical-effects
