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What is a Rainbow?


A rainbow is regarded as one of the most spectacular light shows observed on the earth. A Rainbow is a multicoloured arc made due to the striking of light on water droplets. It is an optical illusion which means that it doesn’t exist in a specific spot in the sky. It depends on where you are standing and the position of the sun or other sources of light.

How to Make a Rainbow?

Sir Issac Newton was the first one to identify that white light was made of all the colours of the visible spectrum. He also showed us that the white light could be split into different colours by a process known as refraction. To refract light, he made us of the prism but it is to be noted that water can also be used to refract visible light. In the experiment listed below, we make use of the concept of density to make a rainbow in a jar. Let us look at the materials needed and the procedure of the experiment in the next section.

Rainbow Experiment


This experiment focuses on density. Here we are making a rainbow in a jar using this amazing concept of density.


  • One or Two Tablespoons.
  • A container of water.
  • Different types of food colouring of good quality.
  • A cup of sugar.
  • A set of Five Glasses.
  • A lot of patience and reliable practice.


  • Place the five glasses. Add three teaspoons of sugar for the first four glasses.
  • Now add a teaspoon of sugar to the glass one.
  • Continue the procedure but with a slight difference. Add two teaspoons of sugar to glass two, three teaspoons of sugar to glass three and four teaspoons of sugar to glass four.
  • Stir until the sugar dissolves completely.
  • Add different types of food colouring to each glasses.
  • Now pour the one-fourth of contains in glass four to glass five.
  • Next procedure is quite a tricky one.
  • Now move on to the next layer. Gently pour the contains in the next layer that is present in the glass three.
  • Note that it should not mix with the first layer present in glass five.
  • One can do this by placing a spoon on the first layer and gently pour the mixture on it so that it can minimise the splash.
  • The slower you do the better will be the results.
  • Repeat the same procedure for glass two and glass three.
  • Ensure that you fill the layers as the same width as the first layer.


Different levels of density are created when the different amount of sugars are added. As you can notice the layer at the bottom of the glass was the heaviest and rest of the layers were placed on the top of each layer. The layers may mix sooner or later, and that may be referred to the concept of dynamics. The effect lasts for a long period of time only when a greater difference in density.

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