This is a representation of how a rainbow is formed - it is not drawn to scale. Refraction plays an important role - when white light from the Sun enters a droplet, it refracts into the droplet, experiences total internal reflection at the back of the droplet, and then refracts back out into the air. Because of dispersion (different wavelengths refract different amounts), different colors emerge in different directions.

Looking at the single droplet, think about which color, red or violet, you expect to see highest in the sky. Then, switch to the two droplets, which gives a better perspective on what is happening - an eye is shown with both red light and violet light entering (the other colors of the visible spectrum would be in between red and violet). Note also that if you move your eye to a different position, you may get a different color entering your eye from the same droplet. This means that we all get our own personal rainbow.

Simulation first posted on 8-29-2018. Written by Andrew Duffy

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This work by Andrew Duffy is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.
This simulation can be found in the collection at http://physics.bu.edu/~duffy/classroom.html.

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