6D40.60 - Optical Doppler Radar

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

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.

  • 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.

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