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Re: low-tech diffraction pattern



What is a shaft encoder? How expensive are they.? Can one
be easily made by students? If so, this would be a good
contribution to the Apparatus section of The Physics Teacher
magazine.

Herb Gottlieb

On Fri, 17 Sep 1999 09:09:38 -0500 Michael Moloney
<moloney@NEXTWORK.ROSE-HULMAN.EDU> writes:
We do a low-tech version of the diffraction pattern of a single or
double slit by using a shaft
encoder and phototransistor. The transistor is housed in a black
plastic block with an
entrance slit on the front. This block is connected to a shaft
encoder and a spring.


When you slide the block through the diffraction pattern (about 3
inches of travel) the shaft
encoder turns so in one pass you have light amplitude vs distance
(well, angle, which is
easy to convert to distance).

This is stuff we did ourselves, hardware and software. The interface
is a BIB (see my home
page for details), so the experiment can be run on a laptop through
the printer port.

Mike


Mike Moloney, Dept of Physics & Applied Optics, Rose-Hulman
Institute of Technology

(812) 877 8302 http://www.rose-hulman.edu/~moloney