As I explained yesterday, We just started looking at v-t graphs that we developed from x-t graphs. We followed the same pattern we did previously and had the students creating and then matching some velocity graphs using the motion detectors. Sometimes I wonder if having the students do this activity is worth the class time, but then I think about (or re-read) Chapter 2 in Arons. He talks about the importance of a direct kinesthetic experience to fully register the concept. It always amazes me that I can have a student perfectly explain a v-t (or x-t) graph, but then not be able to walk it to match it.
Yesterday we the focus was sending parallel light rays into a curved refracting surface. It allowed us to develop many ideas, but most importantly converging and diverging lenses. Yesterday, at the end of the hour, I set myself up for today, by asking what a converging lens would do to light rays that are not parallel. Remember, I’m all about the transitions!
So after a short assessment on Snell’s Law, we answered that question. The flow in the class lead us to the development of how a real image forms, what the characteristics of a real image are, how to draw ray diagrams for lenses and will even set the stage for a thin lens experiment by defining the object distance and image distance. Not all of this was covered today, but I will keep referring back to this setup as we develop each idea.
We used the formation of an aerial image to build these concepts. I first learned about aerial images at a Phox Share session about 8 or 9 years ago from Jeff Elmer and Ed Wyrembeck, both incredible physics instructors. Here is the article published in The Science Teacher that explains the entire thing. Go read it now, I’ll wait. No, really, go read it, especially if you have never heard of an aerial image.
Based on what was shared at that share session and subsequent ones, the set up has been modified. Here is a picture:
Here is another diagramAerial Image Set-Up. When the students see the aerial (real) image for the first time without the paper screen, it blows them away, as it should. It is totally incredible. As you read in the article, one of the important concepts in helping students understand how this image forms is the light cone. The aquarium gets filled with “professional Haze” then covered. The light cones are visible. I’m sure this picture will do it justice.
You should try this. As mentioned above this day sets the stage for quite a bit of optics to come.