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Let's imagine that there is a lamp on the floor. There is a dice on that same floor casting a shadow from our light source, the lamp. Why is it that there are different shades of the shadow phasing from darkest to dullest (darkest being closest to dice and dullest being farthest)?

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Draw a picture of the lamp and the dice. Draw the light rays from the lamp and see where they go. With a little thinking, the answer is visually obvious. – DumpsterDoofus Oct 30 '13 at 23:22
Google umbra, penumbra and antumbra – John Rennie Oct 31 '13 at 9:51
Are you asking for an answer, or are you just day dreaming ? – user26165 Nov 1 '13 at 6:00
up vote 1 down vote accepted

The lamp is not a point source. The smaller the angular size of the source, the narrower is the penumbral shadow region.

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