6C20.35 - Diffraction Around Objects - Circular and Square Aperture

Code Number:
6C20.35
Demo Title:
Diffraction Around Objects - Circular and Square Aperture
Condition:
Good
Principle:
Edge Diffraction
Area of Study:
Optics, Astronomy
Equipment:
Permanently Mounted Optics Rail Setup. Or, Helium-Neon Laser (2 to 5 mw.), Optics Bench, Tape Measure (25 ft.), Washers, Plates with Square Holes, Screen, Diffusing Lens.
Procedure:

This demonstration is permanently set up on one of the optics rails.  We are directing the laser/spatial filter output directly onto the CCD chip in the camera so the laser/spatial filter part will need to be pointed off axis so that the output does not overwhelm the CCD with too much brightness.  Place any of the objects you wish to see onto the front of the camera and observe the diffraction pattern.  After you have lined up the silver mark on the top of the object cap with the top of the camera you may have to rotate the cap slightly to center the object.

Screw the diffusing lens onto the laser and place either the washers or one of the plates with square holes into the diffused beam.  What you should see on the screen is the shadow of the washer or the plate with a series of circular rings where the hole in the washer or the plate is.

References:
  • Bettina Teng, Peter Teng, and Charles H. Hennekens, "A Simple Way to Teach Single Slit Diffraction Based on Edge Diffraction", TPT, Vol. 56, #6, Sept. 2018, p. 380.
  • V. Anantha Narayanan, "Low-Cost Diffraction Experiment", TPT, Vol. 34, #6, Sept. 1996, p. 382.
  • Gordon R. Gore, "Diffraction Photographs with a Laser Pointer", TPT, Vol. 32, #3, March 1994, p. 174.
  • H. Sharifian, H. Tootoonchi, H. C. Bryant, and J. D. Seagrave, "Optical Transforms of the Alphabet", TPT, Vol. 15, #5, May 1977, p. 301.
  • Walter D. Furlan, Genaro Saavedra, and Sergio Granieri, "Simultaneous Display of All the Fresnel Diffraction Patterns of One-Dimensional Apertures", AJP, Vol. 69, #7, July 2001, p. 799.
  • P. Langlois, A. Boivin, and R. A. Lessard, "Production and Use of a Light Beam with an Intensity Proportional to the Distance from the Source", AJP, Vol. 54, #5, May 1986, p. 435.
  • "O-530: Needle, Slit, and Razor Blade", DICK and RAE Physics Demo Notebook.
  • Freier and Anderson, "Ol-21", A Demonstration Handbook for Physics.
  • Jearl Walker, "6.155 Diffracted Alphabet", The Flying Circus of Physics Ed. 2, p. 304.
  • Raymond Bruman, "Long Path Diffraction", Exploratorium Cookbook I, p. 8.1 - 8.2.

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.