We started by working on lots of problems in class. I didn't give any homework at all last night. If we rush, we could finish the unit on Thursday, but why? Break is Friday, and if we take it slowly, we'll finish the unit on Friday and be ready to start the photon model of light refreshed after break. We'll need it; that model is weird.

We whiteboarded lots of diffraction grating and double slit questions, and it seemed that we were confused about when to use one equation and when another. It's a good idea to talk about the assumptions of each of the slit equations. The assumptions behind the slit equation are subtle, and I don't think I realized that until I was challenged so much this year. Thanks, class.

The last two questions we whiteboarded were about what we'd expect to see from one slit or from a small pinhole. We made predictions and then, of course, went to lab to see if we were right. We weren't. But when we talked about what was happening, it started to make sense.

Since so many students will be gone tomorrow, we'll learn the last part of the wave model tomorrow and then practice everything Thursday and Friday.