The science of rainbows
Welcome! I'm excited to dive into the beautiful physics of rainbows with you. Before we start exploring how light and water create these colorful arcs, I'd love to know a bit about your background.
What brings you to learning about rainbows today, and how familiar are you already with concepts like light refraction or reflection?
I have a degree in Meteorology and Climate Science
With your background in meteorology, you already know that raindrop geometry is incredibly clean, with surface tension pulling those tiny falling droplets into nearly perfect spheres. That spherical shape acts as a natural, miniature prism for incoming sunlight.
Your path
Dispersion and the Visible Spectrum
Observer Angle and Geometry
Double Rainbows and Optical Variations
To understand how the magic happens, let's look at the very first step of the process: how white sunlight enters a raindrop.
As sunlight travels through the atmosphere, it moves through the air at a certain speed. But the moment it hits the boundary of a water droplet, it enters a much denser medium. Because water is denser than air, the light waves immediately slow down. This sudden change in speed causes the path of the light to bend, a process known as .
A single white light ray enters a spherical water droplet, refracting downward and dispersing into a spectrum.
I have created a visualization above to help us track this step. Since white light is actually a mix of all the different visible wavelengths, this initial bending does something special: it starts to spread those wavelengths apart because different colors bend at slightly different angles.
Before we look at what happens when this light hits the back of the droplet, how does this concept of light bending in a denser medium sound to you?