6H30.20 - Circular Polarization - Quarter Wave Plate, Polaroid, and Mirror

Code Number:
Demo Title:
Circular Polarization - Quarter Wave Plate, Polaroid, and Mirror
Circular Polarization
Area of Study:
Polaroid, Quarter, Mirror, 3-D glasses, Quarter Wave Plate, and Stand for Quarter Wave Plate.

Place the stand for the quarter wave plate on the mirror and then the quarter wave plate on the stand.  Look down through a polarizer and the wave plate to the mirror.  As you turn the polarizer, the view through the wave plate should go from seeing the reflection to just seeing darkness.

Place the stand for the quarter wave plate over the quarter, and then place the quarter wave plate on the stand.  Look down through the polarizer and the wave plate to the quarter.  As you turn the polarizer, the view should change from seeing the quarter clearly to seeing a dark circle.

Put on a pair of the 3-D glasses and look at yourself in a mirror.  With both eyes open you should see the reflection of your glasses lenses appear very dark.  However, if you close one eye, the reflection through the glasses of the closed eye will appear quite clear and normal.  You can close the other other eye and see the same effect.

The corner cube reflectors will give the same response as the plane mirror demo mentioned above.  Get the corner cubes from either the 6A01.15 - Speed of Light demos box or the 6A10.31 - Corner Cube Reflector Box.  Note that the order should be: corner cube on the bottom, 1/4 wave plate in the middle, and Polarizer on the top.  Look down throught the Polarizer to the mirror and rotate the Polarizer.  

Two mirrors set at 90 degrees ( a true mirror ) will give a different result.  When used with the "mirror - 1/4 wave plate - Polarizer" arrangement as in the demos mentioned above, nothing will happen.  You will have to go with the "mirror - Polarizer - 1/4 wave plate" arrangement to see any effect.  Get the 90 degree mirrors from the 6A10.31 / 6A10.40 demo box, or use the large 6A10.40 mirror demo from the back room.   

  • T. Toepker, "Circular Reflections", TPT, Vol. 51, #2, Feb. 2013, p. 121.
  • P. C. B. Fernando and S. Samarasinghe, "A Technique for Experimentally Observing the Polarization Ellipse", AJP, Vol. 64, #5, May 1996, p. 565.
  • Paul. A. Bender, "Wooden Electromagnetic Waves", AJP, Vol. 53, #3, Mar. 1985, p. 279.
  • "Circular Polarization", Harvard University Natural Sciences Lecture Demonstrations.
  • "Shiny Object Turns Black Viewed Through Linear Polarizer and Quarter Wave Plate", Univeristy of California at Berkeley Lecture Demonstrations.
  • "New Demo with Linear Polarizer and Half Wave Plate", Tap-L Physics Demonstrations.
  • Joseph Frick, "#210 - Circular Polarization", Physical Technics: Or Practical Instructions for Making Experiments in Physics and the Construction of Physical Apparatus with the Most Limmited Means, p. 239.

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.