6C10.15 - Diffraction - Laser and Adjustable Slit

Code Number:
Demo Title:
Diffraction - Laser and Adjustable Slit
Diffraction of Waves
Area of Study:
Optics, Astronomy
Helium-Neon Laser (2 to 5 mW), Optics Bench, and Single Slit (Adjustable).

Put the adjustable slit in the path of the laser beam. As you adjust the slit width observe the changing diffraction patterns.

Another variation of the previous single slit demo is to partially submerge the variable slit in a tank of water.  Measurable differences between the pattern produced through the air as opposed to through the water can be observed and used for calculations.

  • Christopher L. Panuski and Carl E. Mungan, "Single-Slit Diffraction: Transitioning from Geometric Optics to the Fraunhofer Regime", TPT, Vol. 54, #6, Sept. 2016, p. 356.
  • Samuel Hirchman and Eugene Hecht, "What Happens if w< l?", TPT, Vol. 19, #6, Sept. 1981, p. 427.
  • Samuel Hirschman, "Diffraction of Light Apparatus", TPT, Vol. 14, #3, Mar. 1976, p. 180, also A Potpourri of Physics Teaching Ideas - Optics and Waves, p. 233.
  • Mario Iona, "Comments About Slit Diffraction", TPT, Vol. 10, #6, Sept. 1972, p. 323.
  • "O-505. Fixed, Variable & Finger Slit", DICK and RAE Physics Demo Notebook, 1993.
  • G. D. Freier and F. J. Anderson, "Ol-7", A Demonstration Handbook for Physics.
  • Robert Ehrlich, "Q.10. Variable-Width Slit Using Razor Blades", Turning the World Inside Out and 174 Other Simple Physics Demonstrations, p. 202 - 203.
  • Paul Doherty and Don Rathjen, "Diffraction", Exploratorium Science Snackbook, p. 38.1 - 38.2.
  • Joseph Frick, "#191 - Experiments on Diffraction", Physical Technics: Or Practical Instructions for Making Experiments in Physics and the Construction of Physical Apparatus with the Most Limmited Means, p. 222.

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