The student is shown various snapshots of tree trunks lit on different sides (showing different 'phases' of the tree trunk), as well as a diagram of the observer of these trees. The photographer is placed at various angles with respect to the sun and the tree in the diagram (each position is labeled), and the student is asked to determine, based on the photo of the tree, at which position was photographer standing when the picture was taken.
keywords: tree, photographer, snapshot, sun, phase
swf file: ca_lunarcycles_treephases.swf