How to make a rainbow at home

One of the most striking optical phenomena is the decomposition of white light into separate monochromatic lights of different colours. This phenomenon is known as refraction of light, and usually occurs when a beam of light passes through an obstacle that forces the light waves to separate, forming the well-known rainbows. Today, we will look at how the refraction of light works, making a rainbow at home.

refraction of light


- Cooking container (preferably glass).

- Flat mirror (vanity mirror type).

- Good power torch.

- Plasticine.

- A piece of cardboard (optional).

How to create our rainbow

The first thing we are going to do is to place ourselves in a room that we can darken completely. Once there, we fill the container with water and place it on a table.

Then, with the help of the plasticine, we fix the mirror in the water at an angle of 45 degrees. We must take into account that part of the mirror must protrude out of the container of water.

Now, optionally, we can create a circle of cardboard with a small hole in the centre and place it over the lantern lamp to further enhance the beam of light.

We direct the light beam on the mirror and we will see something really surprising, the reflection of the light will turn into a wonderful and colourful rainbow.

Refraction of light

How it works

Refraction of light is a phenomenon that occurs when a beam of light or wave passes through a material medium different from the one it is in. If this wave passes obliquely over this new surface, it is deflected into separate rays with different wavelengths that show different colours to the human eye.

In the case of our experiment, the light passes through the water changing its speed considerably and then reflects off the mirror obliquely, changing speed again. These changes in velocity produce deviations in the direction of light propagation, known as refraction of light. Each independent ray has a different wavelength and it is for this reason that they take on different colours.

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