Activity 8

Polarized Light

Procedure

• Gather these items from your Optics Kit:
  • the polarizers (small dark rectangles)
  • a flashlight
• Look at a light source with both polarizers held together. Rotate one and notice the transmitted light intensity decrease. Maximum decrease is when the polarizers are at 90° -- crossed polarizers. Look at the blue sky in a direction at right angles to the sun.
• Look through one polarizer at the image of the sun, reflected from a glass surface. Rotate the polarizer and note the intensity change.
• Look through one polarizer at a flashlight and note that the flashlight source is not polarized (no change in intensity as the polarizer is rotated). Then look at the flashlight beam reflected off a glass surface and rotate the polarizer. A portion of the reflected light is polarized.
• Most light sources are unpolarized except for
  • sunlight reflected off water (as above).
  • the blue sky (hold two polarizers side by side at 90° to each other. Rotate the pair and compare the variations in transmitted intensity.)
  • lasers. If you have a laser pointer, aim the laser at a wall or paper, place the polarizer over the laser head and rotate it. In one orientation the beam intensity almost vanishes.
  • Can you find any other examples?
• Look through two crossed polarizers with a stretchable piece of plastic between them. Pull the plastic holding one end. You will see an increase in transmission and even colors because the plane of polarization rotates as it passes through the plastic.

To read about light sources go to the Sources of Light Readings

To read about color theory go to the Composition of Color Readings

To read more about polarized light and polarizers go to the Polarized Light Readings