A few weeks ago we proved light behaved as waves since it produces diffraction patterns after going through 2 slits.  Today we investigated the particle nature of light.  I told the students about the photoelectric effect and how it could not be explained with classical physics and led to the idea that the energy of light was quantized (comes in discreet packets).  We also talked about blackbody radiation and how Max Planck also came to the conclusion that the energy of light must come in little packets because classical physics failed to explain the blackbody radiation curves.  These videos explain some of this.

Trying to replicate the typical photoelectric effect experiment in one’s home is not terribly easy and I wasn’t sure I could do it. But after a quick search I found this video on youtube and there is a link to a pdf with instructions on building the demo, so we built this in class today.

Ours didn’t work as well since we didn’t have the nice thin xmas tinsel, but made our own out of regular aluminum foil.  It just didn’t move as easily as the tinsel. But we were able to see the foil strips loose their charge when we put the UV light on the coffee can.  I happened to have a UV light (black tube in the photo below)  for our fluorescent rock collection. Here’s a photo of one of our set ups.  So its wasn’t a ‘Wow!’ experiment but at least we could see the photoelectric effect in action without spending a fortune.IMG_2757.jpg