Okay, so this is not part of my class today. But I also mentor the science club. Yesterday, I saw a tweet by Rhett Allian : How to Measure the Width Hair With a Laser!( Link ) I knew I had to try it. My set up is below. We were able to calculate 59 um! Pretty good! Since our physics class doesn’t do E/M, we always do a day or two on light in chemistry. I look forward to having students white board particle and wave theories.