Monday, January 26, 2009

2nd lecture in conceptual physics course, atoms and Brownian motion

Last Thursday was my second lecture in the conceptual physics course, and the first "real" lecture in terms of physics concepts I'd want the students to remember. I liked how Feynman started out with atoms in his lecture series, so when I started this course, I figured I couldn't do any better than he did. (Although I was recently told by a leader of physics education at U. Minnesota that Feynman's lectures were not effective at all in terms of the learning of the Cal tech students...whoops!) I had assigned the students some reading from Feynman's lecture and also from our textbook about the structure of matter.

I've posted the lecture slides on Slideshare. Before getting into Brownian motion, we did a brainstorming exercise where students suggested things that are in the room, and I tried to classify them in real-time using powerpoint on the overhead projector. By the time we'd finished, the students had come up with many of the things which we'll study this semester and I had tried to classify them in terms of concrete versus abstract and complex versus fundamental. I didn't tell the students the classification system, and they were able to guess what it was after watching me file things away. I don't know if this exercise accomplishes much, but the students seemed engaged. At the end, I pointed out concepts on the page and how they were interconnected and there is no obvious order in which to approach the concepts. I then used this an explanation for the order in which we're approaching things: matter, waves, light, sound, etc.

In terms of Brownian motion, I like the "molecular motion" overhead demonstration. This is a device that sits on top of a regular overhead projector and has a corral that can shake ball bearings. Unfortunately, I didn't get to practice with the demo, and the ball bearings I chose were not well shaken at all. I'd wanted to demonstrate Brownian motion by putting a big ball bearing in with a bunch of small ones, but I pretty much crashed and burned. Hopefully the Brownian motion applets we'll see tomorrow will make up for this. I definitely got lots of laughter, and being laughed at is better than being slept at, in my opinion.

The laser speckle demonstration worked very well in my opinion. I described this a bit in my previous post. As far as I could tell from a show of hands, everyone in the entire room could easily see the shimmering laser speckle pattern on the wet paint. We'll revisit this again later in the semester when talking about interference. Thank you to Dan Ralph @ Cornell Physics for showing us this demo back when I was in grad school!

I'm not sure whether students enjoy the discussion of scanning tunneling microscopy or not. The reason I include it is because I think it's yet another great demonstration of the existence of atoms -- you can practically see them.

Tomorrow's lecture will be about Brownian motion (discussion of homework question, applets) and introduction to energy and conservation of energy. The in-class demos will be the "rattleback" and the nose basher.

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