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Code Number: 6D30.35
Demo Title: Thin Film Interference - HeNe Laser and Glass Plates or Wedges
Condition: Good
Principle: Thin Film Interference
Area of Study: Optics
Equipment:
Two Glass Plates separated by a width of tape, Helium-Neon Laser (2 to 5 mw.), Diverging Lenses, Optics bench (in place of Stand and Holder), Concave Mirror, Focusable Laser Pointer.
Procedure:
Screw the lenses onto the laser for a large divergent beam. Point this at the angled plates. Observe the reflected patterns on a screen. The interference patterns can be altered by squeezing the plates together.
NOTE: The optical flat is in 6D30.10 - Newtons Rings box.
The concave mirror is thin plastic that will have reflections off of the back and front surfaces. This will produce interference patterns on a screen located at least 3 meters from the mirror. The laser used for this is a focusable laser. Change the focus to give the best pattern in the particular room you are in.
References:
- Yi-Qi Xu, Peng Jiang, Yan-Ling Li, "Simulation of Wedge Interference Via GeoGegra", TPT, Vol. 62, #1, Jan. 2024, p. 37.
- Michele D'Anna and Tommaso Corridoni, "Thin Film Interference: An Experiment with Microwaves and Paraffin Oil", TPT, Vol. 53, #8, Nov. 2015, p. 475.
- Thomas B. Greenslade Jr., "From our Files: Laser Interference by Convex Mirror", TPT, Vol. 41, #4, Apr. 2003, p. 250.
- Lewis Epstein, "Dakin's Crazy Interferometer", AJP, Vol. 39, #11, Nov. 1971, p. 1384.
- Uri Oppenheim & Joseph H. Jaffe, "Interference in an Optical Wedge", AJP, Vol. 24, #9, Dec. 1956, p. 610.
- O-455: "Air Wedge Between Glass", DICK and RAE Physics Demo Notebook.
- T. Kallard, "Interferometer for Measuring Parallelism and Small Wedge Angles", Exploring Laser Light, p. 120.
- T. Kallard, "Thin Film Interference Using an Air Wedge", Exploring Laser Light, p. 132.