We looked at diffraction gratings again. Since about 1/3 of my class was gone Thursday and Friday for various competitions (mostly robotics), we built on Thursday and Friday today in class to make sure everyone is at the same place. So we used the better diffraction gratings today and different laser colors. (I love blue lasers. So cool.) We also whiteboarded some of the fundamental questions about how double slit interference works. Today was a good day, but not a day packed with material. That's fine; we should finish the unit this week, right before going on Spring break, so we can start Modern Physics when we get back.