- Sections
- A. General Materials & Mathematics
- B. Statics
- C. Kinematics & Dynamics
- D. Rotational Mechanics
- E. Gravitation & Astronomy
- F. Fluid Mechanics
- G. Vibrations & Mechanical Waves
- H. Sound
- I. Thermodynamics
- J. Electrostatics & Magnetostatics
- K. Electromagnetic Principles
- L. Geometrical Optics
- M. Wave Optics
- N. Spectra & Color
- O. Vision
- P. Modern Physics
M2-03. Laser Diffraction - Poisson's Bright Spot
Purpose
To demonstrate the Poisson (or Arago) bright spot.
Equipment
Laser with beam expander/collimator and mounted steel ball bearing with screen.
Setup Time
10 minutes.
Images
Description
This is one of the keystone experiments in establishing light as a wave (rather than particles). The laser beam is expanded to around 4 cm diameter and passed around a 1 inch ball bearing which is suspended between two pointed rods. The diffraction pattern with its central bright spot is viewed on a distant screen or using a small screen on the end of the optical rail. ◙There is a fascinating story about the origin of this experiment, the details of which I don't remember, but which goes something like this: Fresnel claimed that if light were a wave there would be a bright spot on the axis of
References
Robert P. Barrett, Letter: Poisson's Circles?, TPT 332, 326 ((1994). ◙Wallace A. Hilton, Arago White Spot, AJP 36 #4, ix-x (1968). ◙John B. Johnston, Projecting Poisson's Spot, TPT 16, 179-180 (1978). ◙T. Kallard, Exploring Laser Light, Demonstrating the Paths of Diffracted Rays, pp. 184-185. ◙C. Harvey Palmer, Optics Experiments and Demonstrations, Experiment B13. Demonstration of Fresnel Diffraction by Circular◙Apertures and Obstructions, pp. 196-198.
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See pagesm2. diffraction circular
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See pagesm3. interferometers
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See pagesm4. thin film interference
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See pagesm6. holograms
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See pagesm7. polarization & scattering
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See pagesm8. optical activity & birefringence
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See pagesm9. elliptical polarization
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See pagesm2. diffraction circular
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See pagesm3. interferometers
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See pagesm4. thin film interference
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See pagesm6. holograms
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See pagesm7. polarization & scattering
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See pagesm8. optical activity & birefringence
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See pagesm9. elliptical polarization