Shadows and eclipse
A shadow is a dark region formed on a screen or wall when an opaque object is placed in front of a light source.
Light cannot pass through a solid object; dark area is noticed on the screen. The dark area noticed on the screen is known as the umbra and the region around the umbra is known as penumbra. Umbra and Penumbra are the two types of shadows.
Umbra (total shadow)
Penumbra (partial showdown).
Diagram
Umbra is a shadow cast by an opaque object between a source of light and a screen. The dark region is umbra.
Penumbra is the area around the umbra. When a source of light is small, the shadow has sharp edges and no penumbra.
When the source of light is larger, a penumbra is formed around the umbra.