Concept of Wave, Wave Motion, Characteristics of Wave motion, and types of Wave Motion
- Wave
A wave is a disturbance in a medium that transmits energy without causing net particle movement. Elastic deformation, pressure difference, electric or magnetic intensity, electric potential, or temperature can all be taken as examples.
A wave is a variation that flows through a medium, which is the most significant component in wave transmission. Although the medium through which the wave travels may experience some local oscillations as it passes, the particles in the medium do not travel with the wave. The disturbance could be a finite-width pulse or an infinitely lengthy pulse sine wave.
- Wave motion
Wave motion is defined as the regular or organized propagation of distortions and deviations from a condition of rest or equilibrium—from one point to another. It is the transmission of energy and momentum from one medium point to another without the actual movement of matter between the two points. Surface waves on the water can be considered as the more familiar examples, but sound and light also travel as wavelike disturbances, and all subatomic particle motion has wavelike qualities. A wave is a disturbance in the medium caused by an equilibrium condition that moves at a finite velocity in a certain space region. Wave motion transmits energy from one point to another, displacing or not displacing medium particles.
Vibrations of elastic media, such as air, crystalline solids, or stretched strings, are the most basic types of wave motion. If the block surface of a metal is struck with a strong blow, the deformation of the surface material compresses the metal at the surface, which transmits the disturbance to the layers beneath. The surface returns to its original shape, and the compression continues into the material’s body at a rate defined by the stiffness of the material. A compression wave looks like this. Many types of wave motion involve the sustained propagation of a localized disturbance via an elastic material.
Characteristics of wave motion
- All of the particles in the medium are affected by the Simple Harmonic Motion, about their mean position, and propagate in the same period and amplitude.
- The particles of the medium vibrate about their mean locations in a wave motion.
- The medium has no effect on the movement of the particles.
- Wave motion is periodic in both space and time.
- In the specified medium, a wave motion moves at the same speed in all directions. The nature of the medium through which a wave travel determines its speed.
Common terminologies used in a wave motion.
- The velocity of a wave: It is the distance traveled by the wave in one second (v =/T). The mechanical properties of the medium through which the wave travels decide the velocity of the wave. The wave velocity is calculated in reference to the medium; the wave velocity changes as the medium moves, e.g., the speed of sound through air changes when the wind blows.
- Amplitude: The maximum displacement of any medium particle from its equilibrium position is the amplitude of a wave.
- period(T): The time it takes for any medium particle to complete one vibration throughout a period is called the period (T) of a wave (T).
- Wavelength: The distance between two consecutive particles of a medium in the same state of vibration is equal to the wavelength (). It’s the product of the wave’s distance traveled divided by its time period (T).
- Frequency: The number of vibrations made per second by any particles in the medium (f = 1/T) is known as frequency (f). Since the frequency of the source is a distinguishing attribute of the wave, the frequency of a wave does not vary when it travels from one medium to another.
- Path difference: It represents the distance between two points measured in the wave’s propagation direction across the medium.
- Phase difference: The time it takes for a wave to travel from one point to another via the medium is measured in time difference (T).
Types of wave motion
Based on the motion of the wave in the space
- One Dimensional Wave: The type of waves that propagate in a straight line are known as one-dimensional waves. For eg: waves are produced on a stretched string.
- Two-Dimensional Wave: The type of waves that propagate on a plane are known as two-dimensional waves. For eg: ripples in the water
- Three Dimensional Wave: The kind of waves that propagates in space are known as three-dimensional waves. For eg: the propagation of light and sound waves.
Based on the transfer of energy
- Standing Waves: standing waves are restricted to a zone with no energy or momentum transfer
- Progressive waves: progressive waves move energy and momentum between the medium’s particles.
Based on the medium of propagation
- Mechanical waves
- Non Mechanical Waves
Mechanical waves: Mechanical waves, often known as elastic waves, are waves that need a medium to propagate. When the wave propagates through the medium, the particles of the medium move in a periodic motion around a mean position.
We can make waves on a string for example. A mechanical wave is created when a point in a medium is disturbed and the disturbing particle interacts with the particle next to it, and its energy is transferred to the next particle due to the inertia of the medium. The perturbed particles revert to their original location due to the elasticity of the medium.
Non-Mechanical Waves: Waves that do not require the use of a medium to propagate are called non-mechanical waves. These types of waves can propagate through a vacuum too. These are transverse in nature. The propagation is based on energy transfer. For example, electromagnetic waves and matter waves.
The mechanical waves are further classified into two kinds based upon the direction of vibration of particles w.r.t the direction of the propagation of the wave.
- Longitudinal Waves
- Transverse Waves
Transverse Waves: The motion in which all points on a wave oscillating along pathways are perpendicular to the wave’s movement is known as a transverse wave. Water surface ripples, seismic S (secondary) waves, and electromagnetic (e.g., radio and light) waves can be considered examples of transverse waves. Because the amplitude of any point on the curve—that is, its distance from the axis—is proportional to the sine (or cosine) of an angle, a sine or cosine curve can be used to describe a basic transverse wave.
Image source::https://www.toppr.com/guides/physics/waves/transverse-wave-and-longitudinal-wave/
Fig: Transverse Wave
Crest: The convex region formed by the maximum upward displacement of the wave is known as the crest.
Trough: The convex region formed by the maximum downward displacement of the wave is known as the trough.
Characteristics of Transverse waves
- The crest and the trough form the transverse wave.
- The motion of the wave is perpendicular to the motion of the particle.
- The wave is divided into alternate crests and troughs when the wave passes through the medium.
- The crests and troughs of a transverse wave form a succession of crests and troughs.
- The wavelength is the distance between two successive crests or troughs.
- The medium undergoes polarisation.
- This wave is formed in the solid medium due to the elastic characteristic of the solid medium, and a transverse wave is produced in the fluid medium due to the surface tension of the fluid media.
- Energy will begin to flow from left to right through the slinky. As the energy is carried from left to right, the individual coils of the medium will be shifted above and downwards.
Longitudinal Waves: Longitudinal waves are the waves in which particles of a medium fluctuate around their equilibrium position in a direction parallel to the direction of propagation of the wave. Longitudinal waves can only propagate in a medium with the volume elasticity (or Bulk modulus). The waves travel through a medium in compression and rarefaction in this type of wave motion. Compression refers to a high-pressure area, while rarefaction refers to a low-pressure area. The particles do not follow the wave direction instead, they oscillate back and forth between their respective equilibrium locations. Sound waves in the tube, for example.
Image source:https://byjus.com/physics/longitudinal-waves/
Compression: The high-pressure area where the particles of the particles are crowded together is known as compression. The density in the compression is higher. Compression is also called condensation.
Rarefaction: A rarefaction is a region where the particles in the wave are the farthest apart. The pressure, as well as the density of the area, is smaller. A rarefaction is also known as extension.
Characteristics of longitudinal waves
- The longitudinal wave is a wave in which the particles of an inert medium oscillate about their mean position with respect to the direction of propagation of the disturbance.
- The medium is compressed and rarefied as the wave travels across it.
- The wavelength is the distance between two successive compressions or contractions, or the total distance of compression and rarefaction.
- In a longitudinal wave, compression refers to the region where the particles are closest together, whereas rarefaction refers to the region where the particles are farthest apart.
- There is no polarization of the medium in this case.
- This wave causes an elastic medium to form.
- The period of a wave is the time it takes for it to travel one wavelength, and the frequency is the number of times it happens.
- A wave’s period is the time it takes for it to travel one wavelength, and its frequency is the number of wavelengths per second.
- The displacement of the medium in longitudinal waves is parallel to the propagation of the wave.
- In a longitudinal wave, the wavelength is the distance between two consecutive points in phase. The space between two consecutive compressions or rarefactions is referred to as the wavelength.
- The vibration of the medium’s particles is in the direction of wave propagation for longitudinal waves
Why is wave motion considered to be a doubly periodic phenomenon?
- At every place, a wave-particle repeats its motion after a fixed interval, becoming periodic in time. Waves also repeat themselves after similar distances and become periodic in space. As a result, wave motion is twice periodic. Thus wave motions are considered to be doubly periodic.
References
https://byjus.com/jee/wave-motion/#Terminologies-in-Progressive-Wave-Motion
https://www.cliffsnotes.com/study-guides/physics/waves-and-sound/wave-motion
