Columbia University Physics Lecture Demonstrations


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6C20.1 Poisson's Spot (Arago's Spot)

[Setup Time: 10 Min.] [Current Condition: Good]

Info

A small circular object is placed in front of a laser beam, and the diffraction pattern, with a bright spot in the very center of the shadow, is observed on the screen. Note: this is hard to see in a large class unless students are allowed to come closer to the screen.

Setup Instructions

1. Place the laser mounted on optics bench in front of the second optics bench.

2. Place the lens in the middle of the empty optics bench (in order to disperse the laser).

3. Place the glass slide on the far end of the optics bench such that light from the laser passes through the lens and then strikes the metal balls on the slide.

Parts List

Laser in H. Optics, 1C

Laser Stand in H. Optics, 1C or Black stand bench on back wall

Glass Slide with Tiny Metal Spheres in I. Optics, 1B

Concave Lens in I. Optics, 1B

Optics Bench Rail in I. Optics, 1B

Relevant Simulation

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Other Information

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Real-Life Examples

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More Advanced Reading

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