6A01.30 - Speed of Light - Rotating Mirror

See paragraph one in the procedure section.
Code Number:
Demo Title:
Speed of Light - Rotating Mirror
Speed of Light
Area of Study:
Optics, Astronomy
Pasco Speed of Light Apparatus, 2 meter meter stick, Old Lab Setup with rotating Mirror.

NOTE:  THIS APPARATUS IS DESIGNED TO BE A PRECISION LAB AND NOT AS A CLASSROOM DEMONSTRATION.  FOR OUR DEMONSTRATION PURPOSES IT IS USED TO SHOW THE PARTS AND ORIENTATION OF A "ROTATING MIRROR" SPEED OF LIGHT ASSEMBLY ONLY!!  If you need to set this up as a working speed of light unit, alignment is critical to Pasco Apparatus since we are using a short path length on the order of 160 cm so that it all fits on one table.  Allow at least 2 to 3 hours for setup.  However, once setup is complete the apparatus can be wheeled around without seriously affecting the alignment if moved carefully. 

The description of the old LEYBOLD apparatus setup is shown in picture 3.  

NOTE:  The only real change the LEYBOLD apparatus has from the Pasco setup are much longer path lengths (on the order of 6 to 20 meters) and the use of a screen instead of a measuring microscope.  The extremely long path length and correspondingly long setup make this unacceptable for lecture.

  • Burt Brody, "The Speed of Light: Making an Easy Time of It", TPT, Vol. 41, # 5, May 2003, p. 276.
  • Barbara S. Andereck, "Microwave Hot Spots",TPT, Vol. 28, # 9, Dec. 1990, p. 580. 
  • Alistair Steyn-Ross, Alister Riddell, "Standing Waves in a Microwave Oven", TPT, Vol. 28, # 7, p. 474-476, Oct. 1990. 
  • Rafael Cohen And Hanna Goldring, Martin Harrap, "Measuring Speed of Light With Two Dollar Rotators", TPT, Vol. 18, # 3, Mar. 1980, p. 226.
  • Robert A. DiCurcio, "Speed of Light With a Rotating Mirror and a Laser", TPT, Vol. 16, # 5, May 1978, p. 326.
  • James M. Feagin, "Another Modification of Foucault's Method of Determining the Speed of Light", AJP, Vol. 47, #3, March 1979, p. 288.
  • J. A. Baretta and J. E. Lang, "A Simple Velocity of Light Experiment", AJP, Vol. 46, # 11, Nov. 1978, p. 1189.
  • A. J. Domkowski, C. B. Richardson, Noel Rowbotham, "Measurement of the Speed of Light", AJP, Vol. 40, # 6, June  1972, p. 910.
  • Joseph F. Mulligan, "A Note on the Rotating-Mirror Method for Determining the Velocity of Light", AJP, Vol. 39, #12, Dec. 1971, p. 1537.
  • D. S. Edmonds, Jr., R. V. Smith, "A Velocity of Light Measurement Using a Laser Beam", AJP, Vol. 39, #10, Oct. 1971, p. 1145.
  • Oa-4:  Freier and Anderson, A Demonstration Handbook for Physics.
  • "1, Measuring the Velocity of Light With a Rotating Mirror", Experiments in Optics, Part 2, Klinger Scientific Apparatus Corp., Bulletin 101- 2.
  • PASCO Speed of Light Apparatus manual.
  • Leybold Rotary Mirror manual.
  • Michelson Measurement - Rotating mirror
  • Speed of Light Experiment

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.