(WKBN) – The weather conditions for rainbows have been just right for the past couple of days, and many of you have sent us some wonderful pictures of them from various places. Have you ever wondered how rainbows form?

Well today, you will learn all about one of Mother Nature’s most beautiful spectacles.

First, we have to learn about visible light

The sun is a powerful heat source that is responsible for heating the planet. It is also responsible for the light that humans see on an everyday basis. Simplistically, we can break down the energy produced by the sun into visible light and non-visible light.

Energy in the visible portion of the electromagnetic spectrum is what humans see when the sun shines on the Earth. This light contains the colors that you would see in a rainbow which are: red, orange, yellow, green, blue, indigo and violet.

Explore - Light | NASA
The electromagnetic spectrum with wavelength is shown at the top. The visible portion of the spectrum is between 0.4-0.7 microns or (1×10^-6 meters). Image courtesy of NASA (National Aeronautics and Space Administration).

However, the light we see is not separated into the colors above. It comes as white light. Light in a vacuum travels at a speed of over 600 million miles per hour from the sun to the Earth.

The art of the rainbow is refraction

The speed of light is constant in a vacuum-like outer space. However, the speed of light is reduced slightly in Earth’s atmosphere and is reduced significantly when it travels through a liquid such as water.

When the speed of light changes between two different mediums (air to water, for example) the light is bent in a process that is known as refraction. A common example of this is how a straw appears to bend inside a glass of water. The process of refraction makes the straw appear to be in a different location than it actually is in the glass.

Bringing it all together: The rainbow

You know that the best time to see a rainbow is right after the rain. This takes our two main players: the visible light produced from the sun and refraction and combines them to form a rainbow.

The light from the sun is refracted once inside the raindrop and scatters the visible light into the different colors of the rainbow. This is the cause of the primary rainbow.

Another amazing detail is that this refraction happens twice inside the raindrop which is what produces a double rainbow. This process is duplicated numerous times which is what helps make the rainbow clear to the human eye.

What Causes a Rainbow? | NOAA SciJinks – All About Weather
The double refraction of light in a raindrop. Image courtesy of the National Oceanic and Atmospheric Administration (NOAA).

There are always two rainbows present, but sometimes, the secondary rainbow is too faint to see. The primary rainbow is caused by the first refraction at an angle of 42 degrees, and the colors are arranged from red on top to violet on the bottom.

The secondary rainbow is actually reversed with violet on top and red on the bottom and is at a higher angle because it exits the droplet at 50 degrees.

Alright, enough with the science. All of these details come together to produce a beautiful rainbow like the one below from Guilford Lake in Columbiana County.

Ros, Guilford Lake rainbow
Credit: Ros H., Guilford Lake