- University of Virginia
- Physics Department
A Physical Science Activity
- 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
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.
- 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.
- 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
- 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.
- 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.