How Rainbows Are Formed and How To Make Your Own Rainbow

As the fabulous Dolly Parton once remarked:   

"The way I see it, if you want a rainbow, you've got to put up with the rain."

Photo by Nicholas T

A rain shower's aftereffect which produces that beautiful bow-o-color is all sorts of fun to spy. Have you ever wondered just HOW a rainbow appears?

What Is A Rainbow?

• A rainbow is an arched light which is separated into bands of parallel color stripes.

• When the sun's rays are bent and reflected by drops of rain, the rainbow appears.

• A rainbow is composed of the colors: red, orange, yellow, green, blue, indigo, and violet.

 
How Does It Get Its Colors?

The colors of a rainbow form by the dispersion of light, as the light passes through a prism. The prism distributes the different colors of light according to their wavelengths; so it appears as a spectrum as it travels from the prism to the air.
 
The sun's white light is made up of a spectrum of colors that act like a wave.

Sir Isaac Newton illustrated this by letting sunlight beams pass through a prism and proved that sunlight consists of many colors that the human eye cannot see separately. These colors are the same that compose a rainbow (red, orange, yellow, green, blue, indigo, and violet).

 
So Why Do The Colors Appear In That Order?

Light is bent at different angles for each different wavelength. They appear in the order they do because of the color band.

• Red is least refracted
• Violet is most refracted
• The other colors left are found between red and violet

 
Where Do Rainbows Begin?

A rainbow will always appear directly opposite the sun from the person viewing it. So a rainbow always appears in front of a person whose back is to the sun.
 
Rainbows don't sit at one particular place in the sky. One's perception of a rainbow depends on where the person stands and where the sun's position is in conjunction.

All raindrops reflect and refract light in the same way, but not all of the light from the raindrop will reach the observer's eye, so the light that reaches each person constructs the rainbow for that person.

 
Why Are Rainbows Shaped The Way They Are?

The arc shape that rainbows appear like in the sky are really formed as a circle. The rainbow is circular because when a raindrop bends light, the light exits the raindrop at a 40-42 degree angle away from the angle it entered the raindrop.

• Blues and violets bend at a 40 degree angle.

• Reds and oranges bend at a 42 degree angle.

Rainbows don't actually have ends to them, because they are full circles. We can't observe this because the horizon of the earth is in our way.

If the sun is low in the sky, we can see a half circle. If the sun is high in the sky, we see less of the rainbow.

 Make Your Own Rainbow

To make your own rainbow, use a garden hose or spray bottle. Spray the water in bright sunlight with the sun behind you and the spray in front of you. If the entire circle is not visible you can move the hose around to see the rest of the circle.
 

Photo by me'nthedogs'

"Life is like a rainbow. You need both the sun and the rain to make its colors appear."

Photo by Nicholas T