Untitled Document

Physics Demo Number: 113

Approximate

Run Time: 15 min

Brownian Motion

Demo Description

A dedicated smoke cell with light source and microscope- objective video camera is used to watch jiggling of match smoke particles by air molecules.

Scientific Principles

Evidence of Molecules from their effect on visible smoke particles.

Equipment

Video Microscope Camera
Smoke Chamber Cell
Fiber Optic Tube Light Source
Machined Steel Base Cylinder
Matches (for smoke)

Equipment Location

All in Kit (113) on [H-4-5].

Instructions

Housed in Kit (113) on [H-4-5] are a small smoke chamber cell , a video camera (with a dedicated microscope objective), and a fiber optic light source .

One may use the smoke chamber cell to capture smoke particles as they plume upwards from a recently-extinguished match from the book of matches.

Then the video-camera microscope may be used to view the live Brownian motion of the tiny smoke particles.

One can output the video signal to an interface for projection in the classroom.

The first photo shows the demonstration operating with the tan fiber-optic tube light source as the cell 's source of illumination.

The cell is resting on a dedicated steel cylinder base which has been machined to give the correct height of the cell above the table top and some degree of stability from vibrations.

This cell base tends to optimize ease of quick setup for the microscope and light tubes.

The video camera is sending its signal to the monitor in the right of the photo.

The bright spots seen on the monitor screen are not snow, but individual illuminated smoke particles which were nicely jiggling around in random fashion under the pictured conditions of operation of the apparatus.

The next photo shows a closer view of the smoke cell, microscope objective, light tube , and base.

The third photo shows the apparatus set up for use in SC4327 with the video cable from the camera running to its input to the room VCR projection interface, as shown:

Note that the mechanical input is the left-most one and that the current mechanical VCR setting is F-1, toggled by the mechanical round dial about a foot to the right of the video cable input and on the next rack component up.

The final photo shows the output to the big screen, with the white dots being images of the smoke particles in the microscope.