Concept
When unpolarized light of intensity $I_\theta$ passes thru a linear polarizer whose transmission axis is oriented at an angle θ relative to the transmission axis of a second linear polarizer, the transmitted intensity, I, is given by Malus’ Law:
$$I = I_\theta \cos^2\theta$$
This law can be applied consecutively to any number of polarizing layers, and is useful in explaining the resulting intensity of placing a polarizer at 45° between two crossed polarizers.
Procedure
- Cross two polarizing filters on the overhead projector to prevent light from passing through.
- Insert the third polarizing filter between the two crossed filters at a 45° angle. This allows light to pass through all three filters.
- Experiment by crossing the filters at various angles and noticing the changes in transmitted intensity.
Equipment
- (3) Light Polarizing Filters
- Transmission Type Overhead Projector