I’m working on getting my students used to problem-solving. They’re making progress. It’s baby steps right now, but every little step gets us a little closer. There’s a part of me that wants to ask, “How can you not know how to do this?” but of course the answer is “Because you haven’t taught me to do it, and neither has anybody else.”
Today’s problem was simple. Given a Geiger counter, a ruler, and the knowledge that smoke detectors contain Americium-241, which has a half-life of 432 years, determine the approximate amount of Am-241 in a smoke detector.
It took some discussion of using the half-life in a way they’re not used to, some discussion about flux, and a little help with the dimensional analysis, but they were all eventually able to solve the problem.
Of course the eventual goal is for the kids to be able to set the problem up without help, but the fact that we’re even heading in that direction at all is reason enough to be happy.
It did make their brains hurt a little, but all of the groups eventually got reasonable answers. We calculated about a nanogram, given the assumptions that the detector was detecting all of the particles, that the only emissions the detector was seeing were the alpha-emissions from the decaying americium (which it turns out may not be that great of an assumption), and some very rough order-of-magnitude estimates of the surface area of the detector and the distance between the detector and the source.
Now all I need to do is to gradually wean them from having someone show them how to set up the problems.
