Definition of Shadow
A shadow is a dark area or shape that appears on a surface when an object blocks light from a source, preventing the light from reaching that part of the surface
. For example, on a sunny day, your body blocks sunlight and creates a shadow on the ground.
How Shadows Form
- Shadows are created because light travels in straight lines and cannot pass through opaque objects
- The shape and size of a shadow depend on the position of the light source and the object blocking the light
Types and Characteristics
- The cross-section of a shadow is a two-dimensional silhouette or outline of the object blocking the light
- With a single point light source, a shadow is sharp and well-defined (called an umbra). With a larger or multiple light sources, shadows can have blurred edges (penumbra) and multiple overlapping areas
- Shadows change length and direction throughout the day as the position of the sun changes in the sky
Other Uses and Meanings
- The word "shadow" is also used figuratively to mean gloom, doubt, or a faint indication of something (e.g., "a shadow of a doubt")
- As a verb, "to shadow" means to closely follow or observe someone, such as for training or surveillance
Shadow vs. Shade
Term| Description
---|---
Shadow| The dark shape cast on a surface when light is blocked by an object57.
Shade| An area that is generally cooler and darker because it is protected
from direct sunlight, not just the shape57.
Summary
A shadow is the dark shape or area on a surface where light is blocked by an object, with its appearance and characteristics determined by the light source and the object itself
. The term is also used metaphorically and as a verb in various contexts.
