the partial shadow surrounding a perfect shadow (as in an eclipse) penumbral. ![[Penumbra-Umbra_5454.jpeg]] [Wikipedia](https://en.wikipedia.org/wiki/Umbra,_penumbra_and_antumbra) The **umbra**, **penumbra** and **antumbra** are three distinct parts of a [shadow](https://en.wikipedia.org/wiki/Shadow "Shadow"), created by any light source after impinging on an [opaque](https://en.wikipedia.org/wiki/Opacity_\(optics\) "Opacity (optics)") object of lesser size. In cases of equal or smaller impinging objects, only an umbra and penumbra are generated. Assuming no [diffraction](https://en.wikipedia.org/wiki/Diffraction "Diffraction"), for a [collimated beam](https://en.wikipedia.org/wiki/Collimated_beam "Collimated beam") (such as a point source) of light, only the umbra is cast. `Concepts:` `Knowledge Base:`