Rainbows are magical and one of nature’s most beautiful displays. All you need is water and sunlight and you have the ingredients to something that can take your breath away. Everybody loves seeing a rainbow but do you ever stop and wonder, what is a Rainbow? and how it is formed? In this article we will try and answer these questions.
To put it simply, rainbows are basically reflections of sunlight through millions of tiny raindrops. White light such as the light beams from the sun is made up of 7 different colours. These colours are Red, Orange, Yellow, Green, Blue, Indigo and Violet and the will always appear in the same order.
Rainbows are formed when the light from the sun is split up or refracted into the different colours of the spectrum when it hits millions of drops of water such as rain or a mist from a water fall. Lets say a drop of rain is similar in shape as a sphere. When a beam of light hits that that sphere the light bounces off the inner surface with all colours bouncing and exiting the rain drop at different angles.
When sunlight enters a drop of water it starts to slow down and bend slightly and change direction. This is the action we call refraction. All colours travel at different wavelengths. The colour red has the longest wavelength and travels faster in water then the colour violet which has the shortest wavelength. All other colours in between all travel at different speeds and this is why they are seperated and bounce off at different angles. The incoming beam of white light is separated into a spectrum of colour when it hits the water. We call this dispersion.
Why are Rainbows arched in shape? Well, they aren’t actually an arch. They are actually a circle and what you are seeing the part of the rainbow which is above the horizon. The closer the sun is to the horizon behind you, the more of the circle you will see because of the angle of the light. However… If you are high enough in a plane you might be lucky enough to see the full circle.
Double rainbows occur when you see a second less prominent rainbow above the main rainbow in the sky. What makes these extra special to view is you will notice that the colours of the second less bright rainbow will have its colours inverted. This simply occurs because the light is reflected twice within raindrops.
Upside down rainbows.
These are a little more rare to see. These are foremed in a similar way to your usual rainbow except the sunlight gets bent in ice crystal high in the sky rather then raindrops falling to earth. If you are lucky enough to see one they look like a coulourful smile in the sky.