What would a bug sitting just inside the sharp shadow made by the clear bulb see, looking back at the bulb?
The bug would not be able to see the filament of the clear light bulb, because no light from the bulb arrives where it is. That is why shadows are dark!
What would the bug see if it moved across the edge of the shadow into the lit area?
It would see the whole filament of the light bulb.


The page about shadows

Copyright 2001 J. P. Straley and S. A. Shafer