We're going to be splitting white light into all its component colors using three household items: a compact disc, dishwashing liquid, and a hose. Each experiment will split light through a different color separation process, including dispersion, interference and diffraction.

• A Compact Disc

• Dishwashing Liquid and some Bendable Wire (or a bubble blowing kit)

• Hose with Flow-rate Attachment

• A Sunny Day

1. Get a compact disc and look at the reflection of a window or light bulb through the back of the CD. Notice all the colors? If the sun is bright you can sometimes adjust it to just the right angle to produce a rainbow on the wall.
2. For the next example of splitting up white light you're going to need to make some bubbles. Either use a bubble blowing kit or make a small (1 inch) loop out of wire and mix up some dishwashing liquid with water. Then dip the loop into the mixture and blow through it. Now find a dark surface and rub some of the bubble mixture over it. Blow your bubble so they fall onto the surface (they shouldn't burst if it's covered in the bubble mixture). Shine a light at the bubbles or let sunlight reflect off them. Look very closely at the surface of the bubbles. You should notice different colors swirling all over the bubble. If you blow gently on the bubble you should get the colors to swirl around.
3. The third example of splitting white light is done best on a sunny day with a hose that can produce a fine mist of water. Stand outside and direct the spray right above your head. Now move around in a circle until you can see a rainbow. Usually it's best seen when the sun is nearly on your back.

You should notice a rainbow of colors in each case. Why you see a rainbow is more complicated however. A different process is happening for each experiment.

First, remember that white light is actually made up of many different colors. And in each case all we are doing is splitting the light up. We'll go through each experiment one at a time.

The Compact Disc: The compact disc has millions of small pits etched into its back surface (this is how the data on the disc is stored) these act together to form something called a diffraction grating. This acts a bit like a mirror except the angle that the light bounces off the back surface depends on what color it is. Therefore when different colors bounce off at different angles they separate out and you can see them individually rather then together (i.e. white). The one bright white object that may only appear to consist of three colors is a TV or monitor with a white screen. This process of color separation is called diffraction.

The Bubble: The thin film of soap on the bubble has a peculiar effect on the light that is being reflected. It will only allow certain colors to be reflected. Which color is reflected depends on the thickness of the soap film. This however changes over the bubble and so different colors are reflected from different parts. Blowing on the bubble also changes the film thickness and will move the colors around. You may have also seen this effect in oil on water, where the oil forms a very thin layer on the water. Binoculars and camera lenses are often coated with films to stop light being reflected when it hits the glass. However you can't make a film that will transmit all colors so some will still reflect. This is why they can appear to have a funny color. This process of color separation is called interference.

The Mist: The water spray acts just like rain on a sunny day to form a true rainbow. The light entering the water bounces around and is reflected back out of the drop. However, remember that as light enters water or glass it gets bent? Well, different colors are bent by different amounts of light. Therefore different colors come out at different angles. This is the same effect as what goes on in a prism. This process of color separation is called dispersion.

Want to Learn More? Read an article related to this activity:

• Color and Light

• Sources of Light

• The Composition of Color