How to Make a Rainbow

Co-authored by Bess Ruff, MA

Last Updated: March 6, 2023 Fact Checked

Isaac Newton is credited with being the first to show that white light is made up of all of the colors of the visible spectrum. He also showed that this light could be split into its different colors by a process called refraction. To refract light, he used a prism, but water can also be used to refract visible light. The product of refracting white light is a rainbow, just like the ones you see in the sky.

Method 1

Method 1 of 3:

Refracting Light with a Prism

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Get a prism. There are different types of prisms that manipulate light in different ways. You will need to get a basic prism, also called a refractive prism. This type of prism will allow the light to bend in a way that splits it based on its wavelength. In other words, shorter wavelengths bend more, and longer wavelengths bend less. This creates a rainbow as the light exits the prism.^{[1]
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- You can buy a prism at a science supply store, a hobby store, or online. Basic prisms are relatively inexpensive.
The prism operates by splitting a beam of white light into its component colors. To see this, you will need a high-intensity light source. Put the prism by a sunny window or outside on a sunny day.^{[2]
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Make sure that there is nothing blocking the light from reaching the prism. As the light passes through, it will bend and be split into a rainbow. It might be easier to see if you aim the prism at a white wall or a white piece of paper.^{[3]
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Method 2

Method 2 of 3:

Passing Light Through Mist

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Usually, rainbows are seen in the rain. That is because there are many water droplets falling through the sky refracting the sun’s light. To mimic that, you should find a source of water that can be moved. A water hose or a spray bottle will work nicely.^{[4]
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A stream of water is not ideal for creating a visible rainbow. Instead, you want a mist of water that the sun has to pass through. You can create this mist by holding your thumb over the end of a water hose, or turning a nozzle to the “mist” position.^{[5]
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Once you have a steady mist, turn so that the sun’s light passes directly through the mist. This will allow the sunlight to be refracted by the small droplets of water. You will see the rainbow form in the mist.^{[6]
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Method 3

Method 3 of 3:

Shining Light Through Still Water

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Fill a clear glass with water. Get a glass that has smooth, clear edges. Textured, colored, or patterned glass will impair the results. Fill the glass all the way to the top and try not to spill any of the water.^{[7]
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- Alternatively, you can put the water in a tub or other container. If you do this, place a mirror in the container and submerge it halfway at a 45 degree angle.^{[8]
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The light should shine through the top of the glass and directly hit the surface of the water. The light should shine out the side of the glass, and a rainbow will be visible. The water causes the light to refract much in the same way that a prism does.^{[9]
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Use a backdrop if you’re using a tub and mirror. If you are struggling to see the rainbow, position the glass so that it shines onto a white wall or a white piece of paper. This backdrop will make it easier to see the rainbow. You can use other colors, but this might not be as effective.^{[10]
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- If you are using a mirror in a tub, place the paper above the mirror to see the light when it refracts.

References

More References (1)

↑ http://www.sciencekids.co.nz/experiments/makearainbow.html

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How is a rainbow created?

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A rainbow is formed when white light is dispersed into its component colours which are red, orange, yellow, green, blue, violet and indigo. You usually see a rainbow after rain or at places near a waterfall because water droplets are suspended in the air, causing sunlight to disperse.

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Can you make a rainbow indoors without using sunlight, a mirror or glass?

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A disc or a CD has a film that makes rainbows when in contact with strong light.

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Why do I need sunlight in order to create a rainbow?

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The light emitted from the sun has white light, which is actually a mixture of different colors. When the sunlight refracts with the water droplets in the air, the white light disperses in form of different colors of the spectrum.

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