RAINBOWS

A rainbow is considered to be one of the most spectacular light shows observed on earth.  The "bow" of the rainbow means a group of nearly circular arches of color, all having a common centre.  We see a primary rainbow all of the time.  We rarely see a secondary rainbow which arises from internal reflections.

A rainbow begins when sunlight strikes the front of a raindrop. The entering white light is refracted or bent and separated into its component colours. These colours then bounce off the back of the drop and are bent again as they leave the drop behaving as if they had passed through a prism.

 Why are the different colours formed? Each of the colours present in white light are bent a different amount in passing through the drop. The red bends the least and violet bends the most. The rest of the colours lie in between. The result a red, orange ,yellow, green, blue, indigo, violet colour spectrum.

 The only portion of the colored light you get to see is the color directed at an angle that actually strikes your eye. So, each drop brings one and only one color to your eye. Two people located at different positions will see different colors coming from the same drop. A drop that brings you a speck of red light may in fact bring me a speck of green or violet light.

The location of each colour reflected off the back of the drop and striking your eye is always at a fixed angle measured from a line between your eye and the sun. This angle is approximately 42° measured to the top of the red band and approximately 40° to the bottom of the violet band.

 


This is a rainbow made by firehoses being sprayed across a lake.

Rainbows are only seen when the sun is directly behind you, low in the sky, and there is a rainfall or mist in front of you. This means the center of the rainbow is always located along a line down your shadow.

Try watering your garden with your back to the sun. Use a misting nozzle or cover the end of the hose with your fingers. Squirt the water down your shadow and there will always be a rainbow for you to see. Wave the hose around to see the full rainbow. It sure makes watering a lot more fun!

If you only see the left half of the rainbow move left or spray more to the right. If you see only the right half, reverse the instructions. If the sun is high in the sky, you will see a slanted rainbow that you will be standing in. How do you know if you are doing it right? That is easy you will see a rainbow!

After you have made your own rainbows you will come to realize we are always surrounded by them. All you need to make them visible is the magic dust of a spray of water when the sun is out.