6H30.10 - Polarization - Three Polaroids

Code Number:
Demo Title:
Polarization - Three Polaroids
Observation of the polarization ellipse
Area of Study:
Optics, E & M
Three Polaroids

Place two circular Polaroids on the overhead in the regular manner and set for extinction.  Insert the third sheet between these two and show that now some light will pass.

See the "Bauman" and "Rossing and Chiaverina" references below for the Quantum Mechanical explanation of why the insertion of a third polarizer BETWEEN two crossed Polarizers allows light to pass.

  • Seymour Charas, "Interference and Polarized Light", TPT, Vol. 26, #9, Dec. 1988, p. 570. 
  • Robert P. Bauman and Dennis R. Moore, "Classical Demonstration of Polarization", TPT, Vol. 18, #3, Mar. 1980, p. 214.
  • "Transmission of Light Through Polarizers in Series", TPT, Vol. 4, #4, Apr. 1966, p. 192.
  • P. C. B. Fernando and S. Samarasinghe, "A Technique for Experimentally Observing the Polarization Ellipse", AJP, Vol. 64, #5, May 1996, p. 565.
  • Bill Franklin, "How Can Light Get Through Crossed Polarizers", Teaching About Color & Color Vision, 1996, p. 3D-3.
  • T. D. Rossing and C. J. Chiaverina, "7.1, Polarization By Selective Absorption", Light Science, Physics and Visual Arts, p. 152 - 155.
  • Martin Gardner, "A QM Paradox", Science Tricks, p. 68.

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