Colorful and visually interesting demonstration showing the interference pattern produced by light reflecting off of a soap bubble.

To show the interference fringes produced by a thin soap bubble.

In box labeled 'Thin Film Interference':

• 10cm diameter ring
• lens
• solution

Additionally:

• 35 mm projector
• various stands and clamps

A solution is made out of dish soap, water, and glycerin (to help prolong the life of the bubble). The metal ring is dipped into the solution (a pie plate works well to hold it) and placed into the test stand. The projector is aimed at the bubble film and the reflection is focused onto a distant screen using the lens.

Students must be reminded that the lens has inverted the image. The thinnest portion of the film will therefore be seen at the bottom on the screen as an extended black area just before the bubble breaks.

General Location: There are many parts for this demo and nothing is specifically set aside. There are many pictures below that will hopefully aid in constructing this demonstration. This demonstration could be made with simple house-hold products. The projector is found in the blue closet floor. Clamps and such can be found at the back of the room, while glycerin can be found in the fume hood. Updated on: 01/13/17