Wave (physics)
In physics, a wave is defined as a disturbance that transfers energy through a medium, moving from one area to another. Waves can be classified into several categories, including transverse, longitudinal, surface, electromagnetic, and mechanical waves, each exhibiting distinct behaviors. In transverse waves, particles of the medium move perpendicularly to the direction of wave travel, creating features known as crests and troughs. Conversely, in longitudinal waves, particles move parallel to the wave's direction, resulting in compressions and rarefactions. Surface waves, such as those on the ocean, involve particles moving in circular motions, typically affecting only those near the surface.
Electromagnetic waves, such as light, can propagate through a vacuum, while mechanical waves, like sound, require a medium for energy transfer. Wavelength is an important characteristic of waves, defined as the distance over which the wave's shape repeats, measured differently in transverse and longitudinal waves. Visual aids such as a Slinky toy can effectively illustrate these concepts, demonstrating both transverse and longitudinal wave behaviors. Sound waves specifically are longitudinal waves that consist of oscillations in air pressure, detectable by the human ear or instruments that respond to pressure fluctuations.
Wave (physics)
In physics, a wave is a disturbance that transfers energy in a medium. This disturbance moves from one area of the medium to another area. The categories of waves include transverse, longitudinal, surface, electromagnetic, and mechanical waves. These waves behave in different ways. For example, the direction of travel is different in transverse, longitudinal, and surface waves. The movement of a Slinky toy and a sound wave are two specific kinds of waves.
Categories of Waves
A wave moves through a medium. A medium is a material that consists of particles that interact with one another. Different categories of waves behave in different ways. In a transverse wave, the particles travel in a perpendicular direction to the wave, creating crests and troughs. A crest is the highest point of upward displacement from equilibrium, while a trough is the lowest point of downward displacement from equilibrium. Equilibrium, or the rest position, is the position that the medium exhibits when it does not have any disturbance. In this sense, equilibrium is the condition of a medium that is at rest. A transverse wave’s amplitude is the distance from equilibrium to the crest or from equilibrium to the trough. A transverse wave contains crests and troughs that have an alternating pattern.
In a longitudinal wave, the particles travel in a parallel direction to the wave, creating compressions and rarefactions. Compressions are the areas of the wave that are pressed together with little space between them. Rarefactions are the areas of the wave that are spread apart. In other words, compressions are the areas with maximum density, and rarefactions are the areas with minimum density. As with the crests and troughs of a transverse wave, a longitudinal wave contains compressions and rarefactions that have an alternating pattern.
In a surface wave, the particles move in a circular motion. However, only the particles near the medium’s surface move in this fashion. The movement of particles usually diminishes away from the surface. A wave moving along the surface of an ocean is an example of this type of wave.
Electromagnetic and mechanical waves involve the transmission of energy through a vacuum. Empty space is an example of a vacuum. Electromagnetic waves are able to transmit energy through a vacuum, while mechanical waves cannot do this. The vibration of charged particles creates an electromagnetic wave, such as a light wave. For a mechanical wave, such as a water wave, a medium is needed to transport energy between two locations.
A wavelength is the span of a complete cycle of a wave. In transverse waves, wavelengths are measured by the distance between crests or troughs. In longitudinal waves, wavelengths are measured by the distance between compressions or rarefactions.
Examples of Waves
The movement of a Slinky spring toy stretched out in a horizontal position is a good example of both transverse and longitudinal waves. The coils of the Slinky are the particles. In the equilibrium position, the spaces between the coils are all the same. When the coils on one end of the Slinky are moved up and down, the coils vibrate in a vertical motion, and a transverse wave is created. In this sense, the wave moves up and down across the Slinky. The wave contains crests and troughs, which are the high points and low points of the wave, respectively. Once the coils of the Slinky stop moving, the Slinky returns to its equilibrium. To create a longitudinal wave in the Slinky toy, the coils on one end of the Slinky must be moved back and forth, or compressed. When this happens, the coils vibrate along the Slinky’s length, and a longitudinal wave is created. The wave moves back and forth horizontally across the Slinky. Furthermore, the wave has compressions and rarefactions. The compressions are the areas of the Slinky where the coils are pressed together with little space between them. The rarefactions are the areas of the Slinky where the coils are spread apart. As with a transverse wave, the Slinky returns to its equilibrium once the coils of the Slinky stop moving.
A sound wave is an example of a longitudinal and mechanical wave. This means that the particles travel in a parallel direction to the wave, and the wave is not able to travel through a vacuum. A sound wave is a vibration created when sound collides with the materials in an object. The vibration passes through the object. Like a longitudinal wave in a Slinky, a sound wave has compressions and rarefactions. Specifically, a sound wave has air molecules with compressions and rarefactions. Compressions are the areas with high air pressure. Rarefactions are the areas with low air pressure. Furthermore, compressions are the areas where air molecules are crowded together. Rarefactions are the areas where air molecules are more separated. This points to the fact that air molecules have longitudinal motion. As with all longitudinal waves, sound waves have patterns of compressions and rarefactions that repeat. The human ear, as well as human-made instruments, can detect sound waves by detecting fluctuations in pressure. The ear or instrument can detect high pressure, which represents the arrival of a compression. Low pressure can also be detected, which represents the arrival of a rarefaction. These fluctuations recur, taking place at regular time intervals.
Bibliography
Henderson, Tom. “The Anatomy of a Wave.” The Physics Classroom. The Physics Classroom. Web. 23 Dec. 2014. http://www.physicsclassroom.com/class/waves/Lesson-2/The-Anatomy-of-a-Wave
Henderson, Tom. “Categories of Waves.” The Physics Classroom. The Physics Classroom. Web. 23 Dec. 2014. http://www.physicsclassroom.com/class/waves/Lesson-1/Categories-of-Waves
Henderson, Tom. “Sound Is a Pressure Wave” The Physics Classroom. The Physics Classroom. Web. 23 Dec. 2014. http://www.physicsclassroom.com/class/sound/Lesson-1/Sound-is-a-Pressure-Wave
Henderson, Tom. “What Is a Wave?” The Physics Classroom. The Physics Classroom. Web. 23 Dec. 2014. http://www.physicsclassroom.com/class/waves/Lesson-1/What-is-a-Wave
"Wave." Britannica, 21 Oct. 2024, www.britannica.com/science/wave-physics. Accessed 19 Nov. 2024.