Soap Bubbles
Overview: Soap film is as thin as the visible light spectrum. This results in optical interference and creates an iridescent look.
Supplies: Pipe cleaners, straws, bubble soap
Objectives: As the time elapses on a blown bubble, closely look at the soap bubble film. How does it change? How do the colors change? Does your bubble last long enough for all the color to disappear?
Setup:
- Lay out the pipe cleaners and straws on the table
- Fill a container with enough bubble soap to be able to dip the contraption in the solution
How to run the demo:
- Follow the instructions below on assembling the bubble devices
- Dip the bubble device in the soap
- Blow bubbles!
What’s Happening?
Light transmitted into the film travels further than light reflected off the front surface of the film. When the wave reflected off the front surface of the film lines up with the wave reflected off the back surface the film the waves interfere constructively. When the film thickness is the same as a multiple of a color’s wavelength we can see that color in the film. Different colors are seen as the thickness of the film (or bubble) changes. The film thins as the water in the bubble evaporates and the longer wavelength colors (red) disappear first. When the thickness of the film is less than the wavelength of purple (the shortest wavelength) that area of the bubble will look black.
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