At all key stages consideration of shadows provides a rich source of geometry.
How does the size of your shadow relate to the position of the sun in the sky? At what times of the day is your shadow longest? Why aren't there shadows at midday? These questions will stimulate discussion of straight lines and angles. Encourage pupils to draw diagrams to help explain what is happening. Why is the image in a pinhole camera upside down? What shapes can the shadow of a cube have? What about the shadows of other polyhedra?
How does an overhead projector or data projector enlarge an image?
Why does the image get larger when the screen is moved further away from the projector? How can you calculate the dimensions of the projected image? Discuss how this links to the enlargement transformation.
In Eliasson's light installation, can you explain why the sun's image changes from an ellipse to a circle? Extension: what other mathematical shapes can you generate by intersecting a cone of light with a plane?
Again, pupils should be encouraged to draw diagrams to help explain what is happening. This will involve discussion of angles and similar triangles.
The following websites have teaching materials relating to the geometry of shadows: www.learner.orgteacherslabmathgeometryspaceshadowsshadows_background.h tml www.thirteen.orgedonlinenttiresourceslessonsm_shadow