<P> The umbra ( Latin for `` shadow '' ) is the innermost and darkest part of a shadow , where the light source is completely blocked by the occluding body . An observer in the umbra experiences a total eclipse . The umbra of a round body occluding a round light source forms a right circular cone ; to a viewer at the cone 's apex , the two bodies are equal in apparent size . The distance from the Moon to the apex of its umbra is roughly equal to that between the Moon and Earth ( 384,402 km ( 238,856 mi ) ) . Since Earth 's diameter is 3.70 times the Moon 's , its umbra extends correspondingly farther : roughly 1,400,000 km ( 870,000 mi ) . </P>
<P> The umbra ( Latin for `` shadow '' ) is the innermost and darkest part of a shadow , where the light source is completely blocked by the occluding body . An observer in the umbra experiences a total eclipse . The umbra of a round body occluding a round light source forms a right circular cone ; to a viewer at the cone 's apex , the two bodies are equal in apparent size . The distance from the Moon to the apex of its umbra is roughly equal to that between the Moon and Earth ( 384,402 km ( 238,856 mi ) ) . Since Earth 's diameter is 3.70 times the Moon 's , its umbra extends correspondingly farther : roughly 1,400,000 km ( 870,000 mi ) . </P>
the dark part of a shadow where light from a source is completely blocked is called the
the dark part of a shadow where light from a source is completely blocked is called the
umbra
umbra