Question

why shadows are always dark

Answer 1

A shadow is formed when alight from a light source is obstructed by some object. Relating the 2 statements, when a shadow is formed it happens due to absorption of all light by any object from a light emitting source. As a result a shadow is produced which is due to absorption or absence of light, hence black in color

Answer 2

Hii
If you are In a dark room, with only a red light, the shadow will be green,and if there is a single light source and the shadow is being cast by an opaque object between that light and the surface, the shadow will be black because no light is reaching the surface where it is blocked by the object.

Hope it helps u out..