What Refraction Means in Terms of Rainbows

Refraction occurs when sound or light waves change direction because they change speed. They change speed because they pass through something like glass or water. Refraction is responsible for images being formed in your eye and anything else with a lens. Refractive errors are what eye defects are called and can be corrected with glasses (lenses). A prism is a good example of refraction.

What Refraction Means in Terms of Rainbows?

You can see a rainbow anywhere there are drops of water in the air and sunlight hitting them at a certain angle. Rainbows appear near waterfalls, sprinklers, fountains, and, of course, clouds. When viewing a rainbow from a plane, you see the rainbow as a circle.

Starting at the top, the colors of a rainbow are:

Red
Orange
Yellow
Green
Blue
Indigo
Violet

Sometimes, you can see two rainbows close together. The second one is fainter, and called the secondary bow. The area between the two rainbows is called "Alexander’s Band." It was named after the first person to describe it, Alexander of Aphrodisias, who lived in the Third Century.

What refraction means in terms of rainbows is that the light waves enter the suspended water droplets and bend. The light is refracted twice; once upon entering the raindrop and then again as it leaves. In between the two refractions, it is reflected off the back of the drop. So, it refracts when it enters, reflects off the back, and refracts as it leaves. Red light is refracted at a steeper angle than the blue; therefore, the red can be seen at the top of a rainbow, and the blue is at the bottom, or the inside of the rainbow.

History

Throughout history, men tried to explain scientifically what refraction means in terms of rainbows.

Aristotle, who lived in the Fourth Century, BC tried to explain rainbows. He thought they were caused by clouds reflecting sunlight. He said that light was reflected at certain angles, so the rainbow was not in a certain place, but is seen from a certain place and direction.
The Islamic physicist Ibn al-Haytham, who lived from 965 to 1039, conjectured the rainbow was like a reflection in a mirror. The cloud was like the mirror, with the sunlight reflecting off of it.
Ibn Sīnā (980-1037) explained that the rainbow lay in a mist that was between the cloud and the sun and also, between the cloud and the person looking at the rainbow.
Droplets of rain came into the equation when Shen Kuo, from China ventured his opinion that the sunlight hit the rain to make rainbows.
Finally, the Persian astronomer Qutb al-Din al-Shirazi, hypothesied that the light rays were refracted twice by the drop of water and reflected one or more times between the two refractions.

Ancient Beliefs

Since early times, people have had many reasons as to why a rainbow appears and what it means.

Since it is in the shape of a bow, Hindi people called it the bow of Indra, the god of rain, lightning, and thunder while others called it the bow of Kama, the god of love.
Arabs called it the war bow of the god of thunder, Quzaħ.
The Greeks thought it was a path between heaven and earth made by Isis.
Norse mythology claims it connects the Asgard (home of the gods) and Midgard (home of humans).
Many believe that the rainbow is the sign of a promise.
Christians believe God will never totally destroy the humans on the earth with water.
The ancient Sumerians and Babylonians had the goddess of love and fertility, Ishtar. It was her jeweled necklace that symbolized her promise to never forget the great flood that destroyed her children.

What Refraction Means in Terms of Rainbows