Courses: P1, P4, P14, P16, P40
Smoke from incense is pumped between glass slides, illuminated with a HeNe laser, and viewed through a microscope. The smoke particles exhibit Brownian motion.
Setup: First align the laser -- it must be aimed such that it enters in between the two slides, travels parallel to the surface of the slides, and exits the other side still between the two. Then adjust it so it is centered underneath the objective of the microscope. Now, with the eyepiece in place, look through the microscope and fine tune the aim of the laser to maximize the brightness (just to get it directly lined up with the eyepiece's field of view). This will be easier to see with the room lights dimmed or off.
Insert a piece of incense in one of the rubber stoppers. You want it long enough to burn for at least a few minutes, but short enough that it doesn't hit the far end of the tin when inserted. Light it, blow it out, and insert it into the lower hole on the tin. It may take a minute for the tin to fill up sufficiently with smoke.
Cover the tin's upper hole with a finger and then press down on the rubber top to force smoke through the thin tube and into the space between the slides. Remove your finger from the hole before releasing the rubber membrane. Otherwise you'll suck the smoke back out of the slides. It may take a few puffs to get enough smoke pumped into the cell, and you may want to periodically add another puff of smoke.
You'll need to adjust the focus of the microscope to pick out a layer of smoke that's well lit. As the particles bounce around they may disappear or come into view as they rise or fall into or out of focus. You may need to readjust the focus to get a better view. The microscope has both a course focus knob, and a fine focus knob which is better for this adjustment.
When you have the particles well illuminated remove the eyepiece and replace it with the camera. The camera may have a different focus, so you may need to readjust that.
The software for the camera is AmScope. Click on the MU303 (USB) camera listed on the left to get things started. You can then play with the exposure and gain. Once you have it adjusted you can make the image full screen from the view menu.
