Isaac Newton was the first to demonstrate that white light is made up of all colors of the visible spectrum. He also experimented that it can be broken down into different colors thanks to a process called refraction. For this purpose he used a prism, but it is also possible to use water. This way you get a rainbow, just like the ones you see in the sky.
Steps
Method 1 of 3: Refracting the Light with a Prism
Step 1. Get a prism
Each type of prism acts on the light in a particular way. In this case, you will need a dispersive prism that allows you to change the trajectory of the light by decomposing the light beam according to the different wavelengths. In other words, the shorter the wavelength, the more the light deflects, while the longer it is, the straighter the trajectory. This phenomenon produces a rainbow when light passes through the prism.
You can purchase a prism at a science, hobbyist, or Internet store. Generally, the less complex ones don't cost much
Step 2. Find a sunny spot
The prism fragments a beam of white light in the colors that compose it. Therefore, you will need a light source. It is best to place it near a window exposed to the sun or outside when the weather is good.
Step 3. Get light through the prism
Make sure that nothing is impeding the penetration of light into the prism. When it crosses it, it disperses to form a rainbow. The phenomenon is more evident if you orient the prism towards a wall or a sheet of white paper.
Method 2 of 3: Using Nebulization
Step 1. Locate a source of water
Usually, the rainbow is visible in the rain because water droplets falling from the sky refract the sunlight. To reproduce this phenomenon, you should find a source of water to maneuver. A water pipe or bottle with a vaporizer will work fine.
Step 2. Spray it
If you want to create a rainbow, a continuous stream of water is not ideal. Rather, it is better for you to mist it so that it is crossed by light. You can produce this mist by holding your thumb on the end of a water pipe or, if it has a nozzle, turn it to the function that allows you to mist it.
Step 3. Refract the light with water
Turn the tube so that the sunlight passes through the mist of water. In this way, the rays will be refracted by the droplets and you will see the rainbow form.
Method 3 of 3: Using Still Water
Step 1. Fill a glass of water
It must be transparent with smooth walls. If it's colored, opaque, or textured, the experiment won't work. Fill it to the brim, taking care not to spill the water contained inside.
Alternatively, you can use a tub or other container. In this case, place a mirror in the bowl by tilting it at 45 degrees
Step 2. Let the light pass through the glass
It should come from above and hit the surface of the water directly, forming a rainbow outside the glass. The water refracts the light beam in the same way as the prism.
Step 3. Use a background to improve visibility
If you can't see the rainbow, place the glass so that the light that passes through it is projected onto a wall or sheet of white paper. This background will make the rainbow sharper. You can use other colors, but they won't be as effective.
