How big is a shadow?  That depends on a lot of different things.  Do the activity Shadows #2 in the manual to determine how the size of a shadow depends on the relationship between light source, object, and the surface on which the shadow appears. (Also see the set-up instructions "Shadows Inside" in the Set-Up section in your manual; for some notes about making graphs, go here.) And of course, your notebook will contain your work.

What property of light is responsible for the existence of shadows?
Here are two drawings showing a light bulb, a screen, and an object that is making a shadow on the screen.

Light travels in straight lines, but computer monitors don't know how to show straight lines (unless they are exactly horizontal or vertical)! So you will have to imagine that those stair-steppy things are straight lines, and that this picture shows that the shadow is bigger when the object making it is closer to the source.
Check me:

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