Shadow
A shadow is a dark area formed when an object or organism obstructs light from a source, such as the sun or artificial lighting. Shadows can be observed both indoors and outdoors, and they occur when opaque or translucent objects block light, while transparent objects do not cast shadows as light passes through them. The darkness of a shadow varies based on the type of object casting it; opaque objects create darker shadows compared to translucent ones. Additionally, the size and shape of a shadow are influenced by the distance between the light source and the object, as well as the angle of the light. For instance, shadows cast by the sun change throughout the day, becoming longer in the early morning and late afternoon, and shorter at noon. Historically, these variations in shadows were utilized for timekeeping with devices like sundials, which date back to Ancient Egypt. Understanding shadows can provide insights into basic principles of light and geometry, making them an interesting subject for exploration in both scientific and artistic contexts.
On this Page
Subject Terms
Shadow
A shadow is a dark area that is created when an object or an organism blocks light. Shadows appear both indoors and outdoors. Wherever a shadow appears, there must be a source of light and an object or an organism that blocks the light. The light source may be the sun or a light-producing object, such as a light bulb in a lamp or flashlight. Many inanimate objects cast shadows, including buildings, vehicles, and furniture. Living organisms such as people, animals, and trees also cast shadows.
Overview
Light travels in a straight line until something blocks its path. Only objects that are opaque or translucent can block light. Transparent objects cannot block light because light can pass through such objects. Opaque objects are solid, such as buildings. Translucent objects are partially solid and partially see-through, such as tissue paper. Transparent objects are completely see-through, such as glass. When light reaches an opaque or translucent object, it is blocked from hitting the surface that it would normally hit if the object were not present. This surface may be the ground, a floor, a wall, or a similar surface. The blocking of light creates a dark area—a shadow—on the surface on the side of the object opposite the light source. For example, if a vehicle blocks light from the sun, then a shadow appears on the ground on the side of the vehicle that is opposite the sun. Furthermore, if the light source and/or object is moving, the shadow also moves.
The degree of darkness of a shadow depends on the type of object casting the shadow. Shadows cast by opaque objects are darker than shadows cast by translucent objects. The size of a shadow is dependent on the distance between the light source and the object. Take a chair that is casting a shadow on a wall by blocking the light from a flashlight. If the chair and flashlight are moved closer together, the shadow becomes larger. Conversely, if they are moved farther apart, the shadow becomes smaller. The shape of the shadow depends on the angle of the light hitting the object. With the chair and flashlight example, if the angle of the light from the flashlight hitting the chair changes, then the shadow changes shape.
The sun is another example of how shadows change in size and shape. Shadows change throughout the day based on the position of the sun in the sky. When the sun is at its lowest point in the sky, during the early morning and late afternoon, shadows are large and long. When the sun is at its highest point, at noon, shadows are small and short. These known facts were used in the past to calculate time, primarily with the sundial. The sundial is a device that calculates time by tracking the shadows of the sun throughout the day. Sundials date back to Ancient Egypt.
Bibliography
"All about Light and Dark." Easy Science for Kids, easyscienceforkids.com/all-about-light-and-dark/. Accessed 6 Nov. 2024.
Beal, Janet. "Discover What Causes Shadows: Learn Amazing Science Facts." Catalogs, www.catalogs.com/info/gadgets/what-causes-shadows.html. Accessed 6 Nov. 2024.
"Light Basics." Science Learning Hub, 23 Mar. 2012, www.sciencelearn.org.nz/resources/171-light-basics. Accessed 6 Nov. 2024.
Roberts, Sandy. "The Science of Sunlight and Shadows." Science Friday, 27 Oct. 2022, www.sciencefriday.com/educational-resources/sunlight-and-shadows/. Accessed 6 Nov. 2024.
"What Is a Shadow?" Kinooze, kinooze.com/what-is-a-shadow/. Accessed 6 Nov. 2024.