home google
Ever looked closely at a bubble before?

There's a lot more going on than meets the eye. Take a look! So why do bubbles have so many colors?

The thickness of a soap film is on the order of the wavelength of light, a few millionths of a meter thick at most! As a result you get constructive and destructive interference between the light waves that reflect off the front and back surfaces of the film. For a given thickness of film some wavelengths of light will interfere constructively, other wavelengths destructively, so that one color is emphasized much more than the others (click here for computed fringes one should see in a thin film). As thickness variations, and hence color, move around they can lead to spectacular patterns.
Give it a try!

You can try this on your own. On the soap film side of things all you need is a little dish-washing soap and a wire frame (this can be up to a few inches across). You might, also, try adding some glycerin to the soapy water to make it a little more syrupy. This tends to give you bigger, more slowly moving structures to look at. The commercially available bottles of liquid for bubble-blowing tend to already have some of this added. You then want to try to look at the reflection of a light in the film---the bigger and more diffuse the light source the better! If you want to take pictures you will also need a camera with a decent zoom lens; preferably with a macro setting. Here's a diagram.