Were moving onto "Ray Tracing" diagrams for Convex Lenses. Click the video link on the right hand side of this page to view a sort clip about ray tracing.
Heres a nice link to get everyone started on convex lenses. Also have a look at the applet on the site. It shows you all the different images which can be formed using a convex lens.
If any of you folks find some more interesting links... Post them up ;-)