6H50.15 - Optical Thickness

Code Number:
Demo Title:
Optical Thickness
Optical Thickness & Optical Densities
Area of Study:
Overhead Projector, Microscope Slides and Covers, White Cardboard Plate with Square Hole - In the Optics Table, Black Cardboard Plate.

Put the cardboard plate with the hole in it on the overhead projector.  This is to block off all the light except that being directed up through the glass slides.  As you pile on more slides eventually you will reach a point where they will be optically thick.  Another version of this is to take the optically thick pile and set it on a white and then a black background.  On black the pile looks white and on white the pile will look black.

  • Richard O. Thomas, "A Device for Demonstrating Half-Thickness of Shielding Materials", TPT, Vol. 4, #2, Feb. 1966, p. 77, also A Potpourri of Physics Teaching Ideas - Odds and Ends, p. 316.
  • Ross C. McPhedran, Andrew R. Parker, "Biometrics: Lessons on Optics from Nature's School", Physics Today, Vol. 68, #6, June 2015, p. 33.
  • "A Pile of Plates", Clouds in a Glass of Beer, p. 106-107.
  • C. Harvey Palmer, "Experiment C3: Simple Polarization Demonstrations", Optics - Experiments and Demonstrations, John Hopkins Press, 1962.
  • "4, Polarization by Transmission Through a Stack of Glass Plates", Experiments in Optics, Part 2, Klinger Scientific Apparatus Corp., Bulletin 101- 2.

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