PURPOSE: Demonstrates interference between light reflected by front and rear surfaces of a lens.
DESCRIPTION: This is sort of a dumb experiment, but it explains one of the nuisance effects which is often seen in optics demonstrations. Sometimes funny and undesired circles and patterns show up in your laser interference and diffraction experiments whenever you use a lens. This may be caused by interference of light reflecting off the two surfaces of the lens.
The lens is simply placed in the laser beam, creating the interference pattern on a distant screen.
REFERENCES: (PIRA unknown.) See Demonstration Reference File for relevant paper.
EQUIPMENT: Laser cart with 5 cm focal length convex lens.
SETUP TIME: None.
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