6J11.65 - Pulfrich Phenomenon - Pulfrich Pendulum

See paragraph one in the procedure section.
Code Number:
Demo Title:
Pulfrich Phenomenon - Pulfrich Pendulum
Depth Perception by the Eye
Area of Study:
Optics, Human Biology
Pendulum, dark glass or filters.

Start the pendulum in a motion perpendicular to the viewer.  The viewer should put a dark piece of glass or a filter over one eye.  With both eyes open look at the pendulum and notice that it now appears to be going in an elliptical orbit.

  • Jerold Touger, "Which Observations Should We Believe?: An Activity Using the Pulfrich Pendulum", TPT, Vol. 48, # 1, January 2010, p. 35.
  • Martin Gardner,  "The Pulfrich Illusion",  TPT, Vol. 33, # 2, p. 117, Feb. 1995.
  • Earl Zwicker, "The Pulfrich Pendulum", TPT, Vol. 19, # 8, Nov. 1981, p. 564.
  • John T. McGrath, "The Clever Brain", TPT, Vol. 20, # 2, Feb. 1982, p. 72.
  • W-060:  "Puhlfrich Effect",  DICK and RAE Physics Demo Notebook.
  • Martin Gardner, "The Pulfrich Illusion", Science Tricks, p. 65.
  • Martin Gardner, "The Illusory Pendulum", Entertaining Science Experiments with Everyday Objects, p. 41.
  • Jearl Walker, "7.23, Pulfrich Illusion", The Flying Circus of Physics Ed. 2, p. 314.
  • Raymond Bruman,  "Delayed Vision",  Exploratorium Cookbook I, p. 52.1.
  • Tik L. Liem, "The Elliptical Pendulum Swing", Invitations to Science Inquiry - Supplement to 1st and 2nd Ed. p. 155.

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