Why do shadows change shape when light is shone on them?

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Discussion Overview

The discussion revolves around the phenomenon of shadow shape changes when light is directed at objects, exploring the nature of light propagation, shadow characteristics, and the effects of distance and light source type on shadow clarity. The scope includes conceptual understanding and technical reasoning related to light behavior and shadow formation.

Discussion Character

  • Exploratory, Conceptual clarification, Debate/contested

Main Points Raised

  • Some participants propose that the shape of a shadow is directly related to the shape of the object blocking the light.
  • Others question whether light spreads or remains focused, suggesting that spreading would alter the expected shadow shape.
  • Some participants argue that light can maintain a sharp shape while being observed from different angles, indicating a relationship between light direction and shadow characteristics.
  • It is noted that natural light sources are rarely point sources, leading to shadows that can become blurred as the distance from the object increases.
  • A participant mentions the concepts of umbra and penumbra to explain shadow softening and its implications during events like eclipses.

Areas of Agreement / Disagreement

Participants express differing views on whether light spreads or remains parallel, and there is no consensus on how these factors definitively affect shadow shape. The discussion remains unresolved regarding the conditions under which shadows change clarity and shape.

Contextual Notes

Limitations include assumptions about light source characteristics, the influence of distance on shadow clarity, and the definitions of umbra and penumbra, which are not fully explored in the discussion.

danielhaish
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if you put a light on object you will see shadow in the shape of the object . it would looks like the following picture
ss.png

the blue part is the object.
but if you point a laser or light on specific object you will be able to observe it from differences angles like in the following picture
ss2.png

the black circles are quemen eyes and the red point is leaser .
so my question is whether the light spreading or not because if it does spread i would expect the shadow shape to looks like that
ss3.png

but if it doesn't the light would return only to one angle
 
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danielhaish said:
my question is whether the light spreading or not because if it does spread i would expect the shadow shape to looks like that
Harsh-Light-iPhone-Street-Photos-39.jpg
 
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Dale said:
Harsh-Light-iPhone-Street-Photos-39.jpg
this exactly my point we can see that the light stay in sharp shape but we can observe it from other angles how the lights get to other angles
 
danielhaish said:
this exactly my point we can see that the light stay in sharp shape but we can observe it from other angles how the lights get to other angles
The light gets to other angles by reflection.
 
danielhaish said:
so my question is whether the light spreading or not
Sometimes it does, and sometimes the rays are almost parallel.
 
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Not many natural light sources are points so the light does not all come from exactly the same direction. So the shadow will get more and more blurred as you get closer. Look up Umbra and Penumbra to see things like shadow softening and what you can really see during an eclipse.
Edit: BEG your pardon - the fuzz gets worse as you get further away. If the Moon went way beyond its present distance, (from us) our umbra would be so small that we would never get a total lunar eclipse. The Sun is so much bigger than us.
 
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