Rainbow Legends

SCIENCE OF THE RAINBOWS

By August 17, 2020 No Comments

What is a rainbow?

It is a phenomenon that is caused by the refraction, reflection and dispersion of light as it interacts with water droplets. This results in a multicolored circular arc that appears in the sky. Rainbows that are caused by sunlight are
always visible in the part of the sky that is directly opposite the sun. The conditions need to be optimal with the sun being in one part of the sky and rain falling in another part. You must stand with your back towards the sun in order
to see the rainbow.

Raindrops act like tiny prisms in the creation of the rainbow. The sun’s rays will enter the raindrop as some of the light bends or refracts. The rest of the light bounces off the back of the water droplet where this refracted light goes
back on its original path. It bends as it increases its speed and is reflected back into the water droplet. The light is then refracted into the air and separated into all of its wavelengths and colors. Dr. Raymond Lee Jr., in his book, The Rainbow Bridge: Rainbows In Art, Myth And Science, says that “rainbows are caused because the raindrops do not scatter uniformly in all directions. As the rays strike the drop at various angles, the combined refractions and reflections bend the rays through smaller and smaller angles. You can never touch or reach a rainbow, but you can
touch the water drops that create it.” There are literally millions of these tiny prisms during a rain storm

Why is a rainbow shaped like an arc?

Rainbows are actually a full circle, but if we look at them from the ground, we are only able to see part of it. Under the optimal conditions, if we were to look at it from an airplane, we would be able to see the complete circular rainbow.

How many colors are in a rainbow?

Dr. Raymond Lee, Jr. author of The Rainbow Bridge: Rainbows In Art, Myth And Science says that the number of colors cannot be determined because it depends on how many you can see which are affected by the number of cones in the eyes that are photoreceptors. Typically, the colors have been identified as red, orange, yellow, green, blue, indigo and violet with red being at the top.

What is a double rainbow?

Sometimes, you are able to see a second, lighter colored rainbow above the primary rainbow. The primary rainbow is caused by one reflection inside the water droplet. The secondary rainbow is caused by a second reflection inside the water droplet as the light is reflected when it leaves the droplet at a different angle. That is the reason the secondary rainbow is visible above the primary rainbow. The secondary rainbow will have its colors reversed with red on the bottom and violet on the top, whereas the primary rainbow will have the red on top and violet on the bottom. A
double rainbow has two separate concentric arcs.

What is a lunar rainbow or moonbow?

This rare occurrence is a rainbow that is created by moonlight rather than by sunlight. Because moonlight is not as bright as sunlight, it is often seen as a white rainbow. It is formed from falling water.

What is a supernumary rainbow?

It happens when raindrops that are forming for the primary rainbow are more uniform in shape. It appears on the inner side of the primary rainbow as closely spaced greenish and purple arcs.

What is a spider web rainbow?

Since webs are created by droplets of water, and spider secretions, the rainbow is formed by light diffracting off the web. The light is then scattered in different directions and then is reflected. The factors that influence the colors and
appearance are the angle of the light, the thickness of the web strands and the surface textures of the web.

What is a twinned rainbow or triple rainbow?

This very rare occurrence happens when two rainbow arcs split from a single base. There would be two rain showers happening with different sized drops that combine so that each produces slightly different rainbows which may combine and form the twinned rainbow. The raindrops flatten as they fall. Instead of the colors of the second rainbow reversing as in the double rainbow, they exist in the same order as the primary rainbow which is with the red color on top and the violet at the bottom.

What is a sunbow?

This looks like an arc that resembles a rainbow but is made by sunlight coming through ice crystals, vapor or mist. It is not a rainbow because the sunlight is not coming through water droplets.

What is a sundog?

This happens when sunlight hits clouds of ice crystals and the ice acts as prisms. These are not rainbows because the light is not coming through water droplets.

What is a sun halo, a solar halo or an ice bow? What is a moon halo?

This happens when high cirrus clouds and tiny ice crystals are in the atmosphere. The halo is formed by the light being reflected and refracted and may split into different colors. A lunar or solar halo usually indicates that rain or snow will be forthcoming soon. These are not rainbows because the light is shining through ice crystals.