Optics ** 6H50.10 ** Polarization

Polarization by reflection

Polarization from a scattering tank

WARNING: Please be careful with the laser. Always close the shutter when not in use.

Equipment:

• water tank - main hallway
• milk powder - main hallway
• HeNe laser - shelf 12D
• polarizer - shelf 12C
• a few polarizers to hand around the class - shelf 12C
• support rod for laser - shelf 12D or 4D
• support stand and clamp - main hallway

Theory: A beam of light scattered from a scattering medium will be polarized when the scattering is at 90° to the beam.

Description: First prepare the water tank by mixing in a small amount of milk powder. This scatters the laser beam, making the refracted beam visible. Next, arrange the laser so the refracted beam is easily visible. When the beam scattered at right angles is observed through a polarizer, the beam will alternately brighten and dim as the polarizer is rotated.

The beam can also be polarized before it hits the water by holding a polarizer in the beam. When the polarizer is rotated, the beam scattered at right angles will brighten and dim; this can be seen without having to look through a polarizer.

Setup time: 30 minutes

References: (available in the demo room)

• Meiners, " Physics Demonstration Experiments", 36-6.8 and 6.9, page 1105.
• Sutton, " Demonstration Experiments in Physics", L-127 and 128, page 424.