The shadow cast by an object illuminated by an
extended source of light (for example the Sun)
has two parts:
- An umbral region which is completely dark.
- An observer in this region cannot see any part of the light source.
- The light source is totally eclipsed.
- The umbral region is cone-shaped and tapers down to a point. Beyond this point there is no opportunity for a total eclipse.
- A penumbral section which is not quite as dark.
- An observer sees the light source
partially eclipsed in the
penumbral region of the shadow.
Updated February 11, 2002