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Cheap optics demo kit

The majority of the items are simple to find, and fairly inexpensive. These are the two basic requirements of most teachers out there. I was able to do this for around $35. The biggest trick was to find a way to show the path of light. I don't have a chalk board, so I don't have chalk dust. I teach in a planetarium anyway, and the dust can cloud up my projector over time, it also may cause a problem if allergies are a concern. In the days of yore, it was easy enough to light a cigar, and blow smoke out to show the light path, but we all know how well that would go over today.
     E-cigarettes seemed to offer a solution. It is simply a refillable tube of vegetable glycerin that is heated by a rechargeable battery. It' essentially a very small fog machine. It has no nicotine, with a slightly sweet smell, and lots of vapor that dissipates quickly.

It would be easy enough to simply puff the e-cig to get the result, but you never know what to expect from parents. With that in mind, I had to find a way to to produce the vapor, without promoting smoking. The cheapest way I figured, was to use a siphon pump that you can pick up at Harbor Freight for $3. A camera lens cleaning bulb would be better since the seals were designed for air, but the fluid pump works well enough. The e-cig fits snugly in the tubing, and makes an airtight seal. After a few squeezes, you get pretty good vapor flow.

The 3 laser pointers were $12 and the lenses were $17 on ebay. The bulb was $3, and the e-cig was donated

The laser pointers fit into the 2x4 with 9/16 inch holes. I adding a small notch, which depresses the switches when the pointers are inserted
The beams become clear when using the fogger
Simple set-up
The way the lenses work becomes clearly visible, providing a "neon light" effect.  Lots of "Ooohs" and "Ahhs"

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