The Rainbow- A Beautiful Illusion


Although most of us are already familiar with the basic science relating to the rainbow, surprisingly the more we learn about this colorful phenomenon the more captivating these beautiful layered bands of light become.

What is a rainbow?

We most commonly notice a rainbow in the sky when a substantial amount of rain or fog is present, and rainbows often occur within other circumstances as well- including near waterfalls and seaspray.

White light contains the full spectrum of visible colors, and when sunlight encounters a drop of water in the atmosphere it can refract and separate the colors, like a tiny prism, and then reflect them back to your eye.

If you gaze into the sky at the correct angle (42 degrees) while many water drops are present, wavelengths of light associated with each color arrive at your eye from the collection of droplets. The net effect creates the appearance of a multicolored band of light stretching across the sky, composed of the separated visible color spectrum including: red, orange, yellow, green, blue, indigo and violet.

Do rainbows objectively exist?

A rainbow is literally an optical illusion, because its position is always relative to the position of the observer, light source and horizon. Therefore, the viewing experience is completely subjective, as each person has a unique horizon making it impossible for two people to see the same exact rainbow at the same time.

Is there an “end” to every rainbow?

Contrary to the popular myth passed down for centuries, which promises us gold at the end of each rainbow, this is actually impossible because rainbows are always full circles. In a large grouping of water droplets, the circular symmetry of the drops causes us to see the colors displayed in a circular band in the sky.

Typically, human observers are on land and only able to perceive the light reflected above the horizon, so the full rainbow remains unseen from the ground. Circular rainbows are viewable from certain perspectives above land, such as a mountain or airplane.

As we welcome autumn back to Milwaukee, with its weather fluctuations and myriad of colorful spectacles, be sure to take a second look at the next rainbow that appears among the rain and fog…and consider your unique perception of the beautiful illusion with new perspective.