Penumbra

The penumbra (Latin for mid-shadow) is the portion of a shadow that results from the source of illumination being only partially blocked. Penumbras only occur when the source of light is not a point-source. As the sun is a visible disc, solar shadows have penumbras. The penumbra part of a shadow is contrasted with the umbra part of the shadow in which the light source is completely blocked.

Related Topics:
Latin - Shadow - Illumination - Sun - Umbra

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The part of the penumbra where an annular eclipse is visible is called the antumbra.

Related Topics:
Annular eclipse - Antumbra

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Also, the penumbra is the lighter, fuzzier outer edge of a shadow.

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The shadow is darkest at the umbra, near the object, and weakest at the penumbra, at the edge.

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