What is penumbra?

To determine Sharpness in Radiography concerned with Xray tube focal point

Is one of the distinct parts of a shadow together with umbra and antumbra, created by any light source after impinging on an opaque object

A fringe region if half shadow resulting from the partial obstruction of light by an opaque object.

- the grayish marginal portion of a sunspot.

the Blurred Margin of an Image

The umbra, penumbra and antumbra are three distinct parts of a shadow, created by any light source after impinging on an opaque object. For a point source only the umbra is cast.

the partially shaded outer region of the shadow cast by an opaque object.

 the part of a shadow in which there is a small amount of illumination from a light source.

 blurring at the edges of a structure on a radiograph.

blurring on the edges or borders