What are essential for the formation of shadow on the screen?

For the formation of a shadow on a screen, three essential elements are required: a light source, an opaque object, and a surface (the screen) for the shadow to appear on. The opaque object blocks the light from the source, preventing it from reaching the screen in certain areas. This results in a dark shape or shadow that corresponds to the outline of the object on the illuminated surface. The position and angle of the light source, as well as the distance between the object and the screen, also influence the size and clarity of the shadow.