Today we started physical optics. This is the first truly new unit to all students this semester. The lesson was a series of a proposed scenario; prediction based on current understanding of light; demonstration of the scenario; and finally conceptual, geometric, and mathematical explanations. One lab stand and a laser was all that was needed for the demonstrations. I love have the laser incident on the thin wire and illustrating diffraction on the wall, and students are amazed by the results.
Two excellent questions were asked for which I didn’t have answers. One: when light is destructively interfering and forming a minimum on the wall, where did that energy go? Two: while we observe that light diffracts, as do other waves, why do they diffract? Please feel free to pass along any answers and save me some research (especially, a conceptual explanation of the second question)!