Today, we whiteboarded problems on curved mirror and refraction. And, in both classes, the whiteboarding went quick. And, in both classes, the sticky points were the same—what if we cover half the mirror? why do we have to be careful from where we measure the angle of refraction? How many significant digits should we use? Then we talked more about the law of refraction and when it doesn't give an answer and watched my favorite total internal reflection video.
The class today made me think when is whiteboarding useful. If I know what the questions are going to be, and they are this predictable, does that mean I shouldn't whiteboard? Does that mean my questions are too easy? Does it mean that I should whiteboard and let students come to their own answers through these typical pitfalls?