4D10.10 - Brownian Motion

See paragraph one and two in the procedure section.
See paragraph five in the procedure section.
See paragraph three and four in the procedure section.
See paragraph three and four in the procedure section.
Code Number:
Demo Title:
Brownian Motion
Kinetic Theory
Area of Study:
Heat & Fluids
Video microscope with 100 X lens, Microslides filled with different density Microsphere solutions. Microspheres, Microscope slide and slip cover. Small black & white video camera, barrel lens with 10X objective, attachment with smoke cell, laser or Maglite, matches.

Place the microslide with the desired density of microspheres under the microscope.  Using the 100 power lens you may observe the Brownian motion. 

Poisson Distribution.  THIS WILL TAKE 2 TO 3 DAYS ADVANCED NOTICE:  Prepare a microslide with a high density solution of microspheres.  Set the microslide at an incline for several days or until a Poisson distribution is established in the microslide.  


Put a drop of microspheres ( 1 micron diameter spheres ) onto the microscope slide.  Cover with a slip cover to make a thin even layer.  Place on the microscope and focus.  Small black dots displaying Brownian motion will be easily observable.   It helps to cover the eye pieces of the microscope when operating in the video mode.

A substitute for the microspheres would be to use a dilute solution of milk on a slide.  The globules of fat will show Brownian motion. 


To do Brownian motion with smoke particles you will do the following procedure.  

NOTE: This is much more difficult than using the microspheres and requires constant attention and adjustment.  

Attach the barrel lens to the video camera and then the smoke cell attachment to the barrel lens.  Fill the smoke cell with smoke from a match and illuminate with either the laser or the Maglite.  This will show up fairly well on a TV if you are not very far away, although the contrast will still be fairly poor.  The best way to do this is to video capture a segment of the motion and apply some sharpening and false color, and then project the rendered video.

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  • A-48, Richard Manliffe Sutton,  Demonstration Experiments in Physics,  p. 463.
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  • A-51, Richard Manliffe Sutton,  Demonstration Experiments in Physics,  p. 464
  • Eli Barkai, Yuval Garini, Ralf Metzler, "Strange Kinetics of Single Molecules in Living Cells", Physics Today, Aug. 2012, p. 29.
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  • Griffin & George, " Whitley Bay Smoke Cell XCU-300-T", Instructions.
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  • Tap-L conversation with Gerald Zani, Aug 2005.
  • Tap-L conversation with Sam Sampere, Sep 2007.

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