6D40.60 - Optical Doppler Radar

See paragraph one in the procedure section.
See paragraph two in the procedure section.
Code Number:
6D40.60
Demo Title:
Optical Doppler Radar
Condition:
Excellent
Principle:
Interference of Light
Area of Study:
Optics
Equipment:
Laser or laser pointer, microscope slide or beam splitter, amplifier/speaker with solar cell, mirror on adjustable support.
Procedure:

See also 1H10.35 in Mechanics as this is where the demo is located.

Attach the magnet to the blackboard or metal wall.  Align the laser beam so that it is bounced back into the laser. Place the beam splitter in front of the laser and put the reflected beam onto the photocell.  Turn up the amplifier and then press on the wall or the table holding the apparatus.  A squeal should emit from the amplifier speaker as the wall or table flexes.

An simple version of this demo is to just shoot the laser beam directly into the photocell that is connected to the amplifier/speaker.  Place a microscope slide in the beam between the laser and the photocell.  As you rotate the microscope slide a "whine" will be heard from the speaker.

References:
  • T. D. Nichols, D. C. Harrison, and S. S. Alpert, "Simple Laboratory Demonstration of the Doppler Shift of Laser Light", AJP, Vol. 53, #7, July 1985, p. 657.
  • François Remy, "Doppler Effect: An Optical Experiment", AJP, Vol. 46, #7, July 1978, p. 763.
  • Darrell K. Hutchins, "Optical Doppler Shift Experiment", AJP, Vol. 44, #4, April 1976, p. 391.
  • T. Kallard, "The Optical Doppler Radar", Exploring Laser Light, p. 174.

Disclaimer: These demonstrations are provided only for illustrative use by persons affiliated with The University of Iowa and only under the direction of a trained instructor or physicist.  The University of Iowa is not responsible for demonstrations performed by those using their own equipment or who choose to use this reference material for their own purpose.  The demonstrations included here are within the public domain and can be found in materials contained in libraries, bookstores, and through electronic sources.  Performing all or any portion of any of these demonstrations, with or without revisions not depicted here entails inherent risks.  These risks include, without limitation, bodily injury (and possibly death), including risks to health that may be temporary or permanent and that may exacerbate a pre-existing medical condition; and property loss or damage.  Anyone performing any part of these demonstrations, even with revisions, knowingly and voluntarily assumes all risks associated with them.