The clear bulb makes a sharp shadow, because all the light comes
from one place -- the filament (the photograph on the left doesn't show
this accurately). The light from the frosted bulb comes from all
over its surface.
You should set up this exercise for yourself. There is a worksheet
"Shadows #4" in the Shadows section of the manual that you can use.
When you have finished with these questions, hit the "Back" button
twice
