Polaroids on the Overhead Projector 6H10.10
Optics Polarization Dichroic Polarization

Concept

When unpolarized light of intensity $I_0$ passes thru a linear polarizer whose transmission axis is oriented at an angle $\theta$ relative to the transmission axis of a second linear polarizer, the transmitted intensity, $I$, is given by

$$I=I_0 \cos^2\theta$$

As the second polarizer is rotated, the transmitted intensity varies according to Malus’s Law given above. Note that as $\theta \rightarrow 90°$, $I \rightarrow 0$.

Procedure

  1. Place both filters parallel to each other on the overheard projector.
  2. Overlap the filters.
  3. Notice that polarized light is transmitted through each filter as well as through the combination of filters.
  4. Rotate one filter 90 degrees.
  5. Notice that the light is not transmitted through the combination of the two filters.

Equipment

  1. (2) Linearly Polarized Filter
  2. Transmission Type Overhead Projector