This optics unit is large enough, that I decided to have two exams – one on physical optics and one on geometric optics. Today, was the physical optics exam. Historically, I’ve presented geometric optics before physical optics. This year, to align with the Knight text, I presented physical optics first. Unfortunately, the version of the exam that I copied had a handful of refraction questions! As a result, students ended up with a shorter exam than intended once I told them which problems to skip….