I have the usual lasers and lenses, diffraction gratings and polarizing filters, and this year I can do a double-slit demonstration too. And I can do some electrostatics demonstrations this year, not just the usual magnetic field demos.
A kids' favorite is the Newton's cradle with 1 pound steel balls. It is a bit too battered to be a nice momentum/energy demo (it doesn't keep clacking back and forth for very long), but with bits of paper in the middle there's a nice connection to meteors. Unfortunately the fishing line breaks a lot on that one and the younger kids want to make the balls flail around, so it needs extra supervision.
This year I got a cheap geiger counter, and wonder if some simple demonstrations of radioactivity are in order. Pro: they may not see this again until college, if then. Con: some people freak out easily and fear is contagious. But then people seem OK with the snake demo crowd, so maybe that's OK.
Since I'm alone at the table I have to supervise all the demonstration gear and do the spiel for the current demo at the same time. That's another limit on what I can do.
I've a uranium glass plate that makes the counter sing, but not much else. I could open up a smoke detector (I'm not such a fool as to try to get the source out of the well, though), but I'd probably get in trouble for that unless I posted it. The counter's not sensitive enough to pick up potassium chloride pills, much less bananas. The old thorium lantern mantles haven't been made for years. Any inexpensive suggestions? I can order some uranium ore, but I've already got uranium in the plate.
What would you have gone for? This is indoors, so nothing explosive or flammable, and the age range is 4 to 11 years or so.
A daughter generally does rocks and minerals at a different table. A rocket club shows some of their rockets but doesn't launch anything. A pity. Outdoors we could tether a rocket to wrap around a bar, or try a pinwheel.
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