Materials: Two polarizing filter, cellophane tape, mica, wood.

Building Instructions: Place two pieces of wood close together to hold filter upright. Repeat for other filter. Place mica or cellophane tape between filters and notice colors produced.

Functions and use: Light normally vibrates in all directions but sometimes it vibrate in only one direction – this is called polarized light. It turns out that when light reflects off the road or a car or other object it becomes polarized. That is why polarizing filters are used in sunglasses, it filters out the polarized light that is due to the reflection (this reflected polarized light we call glare). This concept is used a lot in radio astronomy and sometimes in other radiation types as well.

In this demonstration, cellophane tape is placed on a Plexiglas and is placed between two pieces of polarizing filters that are set-up so that they are opposite of each other. The cellophane tape changes the speed of the light as it travels through the tape and this small change allows some of the light to travel through the second filter and creates the colors seen.