University of Virginia
Physics Department

## Polarized Light

A Physical Science Activity

### Student Activity

Materials

• Rope (about 6 ft) (a jump rope will work)
• Panel of wooden fence (4-ft length) (can be constructed from scraps of wood or even cut from a box) (figure 3)
• Polarizing lenses (polarized sunglass lenses)
• Unpolarized light source (any incandescent or fluorescent bulb or sunlight)

Procedure

The first part of this procedure is best completed as a class demonstration with group discussion. The second part can be accomplished in either large or small groups.

1. Run the rope through the section of fencing. Have two students stretch the rope between them at waist height while a third student holds the section of fencing between them so the slats are vertical. The students holding the rope will shake the rope up and down so the oscillations are in the same direction as the slats. The wave will pass through the slats unhindered.
2. The student holding the fence section should rotate it 90° so the slats are horizontal. The wave with up and down oscillations will not travel through the slats when they are in this orientation.
3. Hold a piece of polarizing lens up to a light source so the light is viewed through it. Rotate the lens and notice the intensity of the light does not appear to change.
4. Hold two pieces of polarizing lens up to a light source. Hold one piece stationary but rotate the other like the piece of fence section. Notice the intensity of the light changes as this second filter is rotated. When the lenses are at right angles, no light is transmitted through the pair of lenses. When the lenses are parallel, however, the same amount of light is transmitted, as though only one lens were present.