What is the definition of a shadow?

A shadow is defined as a dark area or shape produced when a body blocks light. This occurs because light travels in straight lines, and when an object obstructs this path, it prevents light from reaching certain areas behind it, resulting in a shadow. The characteristics of shadows can vary in size, shape, and intensity depending on the light source, the object's distance from the surface where the shadow is cast, and the object's transparency and opacity.

Other choices do not accurately capture the essence of a shadow. For example, the first choice discusses light obstruction but lacks the necessary context of a resulting dark area. The third choice refers to darkness within a confined space, which can occur without the involvement of light obstruction. The final option describes a reflection instead of a shadow, as reflections involve the bouncing of light off surfaces rather than blocking it.