From physical model to conceptual model (and ray diagrams)

[Matt Anthes-Washburn]

Hi, all,
I guess I'm a little confused-- it seems like Activity 6 is different from Activity 7, because in activity 6, the rays all originate from a single point, and in Act. 7, they are all parallel. It's a subtle difference, but as I try to think what the analogies are for the ray tracings, it seems they are distinct. In activity 6, we look at all the light leaving a single point, as in the reflected light off the tip of your knows. But in Act 7, they look at parallel rays coming in. What's the analogy? Different points on the nose (i.e. the top, middle, bottom). I suppose this is important, because we talk about the image, and we can see that light from different parts of the object is further apart or closer together. Will students be confused trying to draw ray diagrams with this different view? Should they also draw parallel rays bouncing off a plane mirror (and thus staying equidistant)? What do you all think?
Matt

[Sandy Shutey]

I haven't gotten there yet but I always liked ray tracing from plane mirrors before anything else.  I also like having them find the image behind the mirror and measure it.   It is a real surprise to most students when they can actually find it for a plane mirror and it is a virtural image.

[Paul W. Shafer]

This sounds good and is what we are doing on our worksheets at this time.