Brownian motion relates to the phenomenon that tiny particles immersed in fluid move around randomly. Essentially, this equipment shows that molecules of air hitting the smoke particles move with a completely random motion.
The smoke cell (sometimes called the Whitley Bay cell because of its patterned lens) consists of a clear plastic box with 4mm sockets either side, a 12V lamp and lens. To view the movement of the molecules, you will also need a school microscope.
Use a smouldering piece of paper and pipette to place a small amount of smoke within the cell (the cylindrical chamber) and use a cover-slip to seal it in.
Connect smoke cell to a 12V labpack and place onto the microscope.
Aim the objective lens at the cover-slip and adjust the focus until you can see minute dots of light. Observe the random movements of these particles.
The cell may need to be taken out and cleaned after a few uses as the smoke may affect the light reaching the microscope.
Using a flexcam and projector or television screen not only allows a whole class to see the effect but also can enhance the clarity and brightness of the particles.