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Umbra and penumbra


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Here you have the shadow cast on a screen by a sphere placed in the path of light rays.

The outer or penumbral shadow is a zone where an object blocks part but not all of the light rays from reaching the screen. In contrast, the inner or umbral shadow is a region where the object blocks all direct light from reaching the screen.

You can change  the size of the light  source by clicking on it. You can also vertically drag the sphere that blocks the light..

Click on the source to change its size.

Click and  drag the sphere that blocks the light rays.

Learning goals

  • To distinguish umbra from penumbra.