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# Waves

A wave can be described as a disturbance that travels
through a medium from one location to another location. Consider this example the
first thought concerning waves invokes up a picture of a wave moving across the
surface of an ocean, lake, pond or other body of water. When a pebble is thrown
in a pond, it creates a disturbance and forms ripples which travel together as
a front in a straight-line direction, or the waves may be circular waves that
originate from the point where the disturbances occurs in the pond. The wave is
defined as the energy transferred through medium with regular vibration or
oscillating motion. A few examples of waves are:  water wave, light wave, electromagnetic wave,
sound wave, seismic wave (earthquakes). The waves are classified mainly two types that are longitudinal wave and transverse waves. The sound waves are good example of longitudinal wave which is travelled medium with the use of force. This force is exerted between molecules of the medium. The electromagnetic radiations are transverse waves which also include the light waves. These waves show displacement in the perpendicular direction of the field intensity vector. The quantum theory gives the description of wave properties which includes wave intensity, wave number, wave frequency, energy of wave, wavelength etc. the motion of wave and its full study is physical phenomena. Let’s discuss wave properties and some examples of waves.

One way to categorize waves is on the basis of the direction of movement of the distinct particles of the medium relative to the direction that the waves travel. Waves can be classified into two types Longitudinal Wave and Transverse Wave.

Longitudinal Wave: Longitudinal waves occur when the oscillations are parallel to the direction of propagation. It is a wave in which particles of the medium move in a direction parallel to the direction that the wave moves. A sound wave traveling through air is a classic example of a longitudinal wave.

Transverse Wave: Transverse waves occur when a disturbance creates oscillations perpendicular at right angles to the direction of energy transfer. It is a wave in which particles of the medium move in a direction perpendicular to the direction that the wave moves. The electromagnetic radiations which include light waves are a classic example of transverse waves.

{The quantum theory gives the description of wave properties which includes wave intensity, wave number, wave frequency, energy of wave, wavelength etc. the motion of wave and its full study is physical phenomena. Let’s discuss wave properties and some examples of waves}.

## Wave Definition

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A disturbance causing energy transfer from one location to another location is called a Wave. A medium is a substance or material that carries the wave. The highest point on a wave is called the peak. The lowest point is called the trough. The peak of a wave and the trough of a wave are always twice the wave's amplitude apart from each other. Wave motions transfer energy from one place to another.

There are two modes of energy transfer: (Check Spacing)
1) Particle motion
2) Wave motion (to be in capitals)

A wave is produced when a vibrating source periodically disturbs the first particle of a medium. This creates a wave pattern that begins to travel along the medium from particle to particle. When no particle is transferred from one part of space to other although energy is transferred then we call it wave or simply wave.
The disturbance can be due to natural reasons like wind, air, storm etc. or it can be caused intentionally. During energy transfer of the wave from one point to another, the wave possesses the energy. This energy is called wave energy.

## Waves Properties

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Transmission and media: (spacing) The movement of the wave is mostly rectilinear or in a straight line. A medium can be a bounded medium, a linear medium, a uniform medium, an isotropic and an anisotropic medium. These are also called as the transmission medium such as solid, liquid, gas or plasma that can transmit energy waves. Waves undergo the following phenomena namely reflection, interference, absorption, refraction, diffraction, polarization, dispersion.

1) Reflection: The properties of reflection on a mirror are also followed by a wave. When a wave reflects then the angle of incidence is equal to the angle of reflection.

2) Interference: When waves of equal frequency and nearly equal amplitude are super imposed then the phenomenon of interference occurs. It focuses on two kinds such as constructive interference and destructive interference.

3) Absorption: The property of absorption is also followed during wave motion. It can be absorbed by some surface leading to the change in the type of energy.

4 Refraction: While traveling from one medium to another the wave may change its speed. This property is called Refraction. The amount of refraction is dependent on the refractive index of the medium.

5 Diffraction: The phenomenon of spreading of wave when it passes or emerges from an opening or it bends when it encounters an obstacle is called Diffraction. These effects are more significant if the size of the opening is comparable to the wave’s wavelength.

5 Polarization: A wave oscillating in one plane or direction is called a Polarized wave. It can be circular polarized or plane polarized. We can use the polarization filter for this purpose.
6 Dispersion: The phenomenon of dispersion is also followed by the wave. Dispersion is the breaking into the component colors like when the white light passes through the prism then it is dispersed into 7 colors.

## Wave Speed

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The wave speed is the distance covered by the wave in a given interval of time. It can be said that the speed of a wave is also the wavelength/period.
Wave Speed = $\frac{Distance\ Covered}{Time\ taken}$.The wave speed varies for different types of waves. The Speed of light wave is 3 $\times$ $10^{8}$ m/s. The wave speed is the speed at which a particular Parts of a Wave say, a crust moves through the medium.

## Wave Energy

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During energy transfer of the wave from one point to another, the wave possesses the energy. This energy is called wave energy.Ocean wave energy, tidal wave energy, sound wave energy, green wave energy are the examples.

## Wavelength

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Wavelength is the distance between identical points in adjacent cycles of a waveform signal propagated in space or along a wire. It measures the distance between any two adjacent locations on the wave. This distance is usually measured in one of three ways: crest to next crest, trough to next trough, or from the start of a wave cycle to the next starting point. The size of a wave is measured as its wavelength, which is the distance between any two corresponding points on successive waves, usually peak-to-peak or trough-to-trough.

## Amplitude of a Wave

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Amplitude is the maximum positive displacement from the undisturbed position of the medium to the top of a crest.

Amplitude of Wave is the distance from the center line to the top of a crest or to the bottom of a trough. The greater the amplitude of a wave then the more energy it is carrying. The maximum positive displacement or distance moved by a point on a vibrating body or wave measured from its equilibrium position is the amplitude of wave. The units of the amplitude depend on the type of wave, but are always in the same units as the oscillating variable. When the amplitude of a wave steadily decreases because its energy is being lost, it is said to be damped. So, the greater the intensity of a sound, the greater will be the amplitude.

## The Period of a wave

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The time taken by the wave to complete one vibrational cycle or one oscillation is called  period of the wave. It is related to frequency by the formula,
Time period T = $\frac{1}{f}$where, f is the frequency of the wave.

A Wave Vector will helps  us to describe a wave. Which got both direction (direction of propagation of the wave) and magnitude (wave number or angular wave number).

## Wave Frequency

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The frequency of a wave refers to how often the particles of the medium vibrate when a wave passes through the medium. A part of a Wave refers to how many waves are made per time interval. This is usually described as how many cycles or oscillations made per second. If twenty oscillations are made per second, then the frequency is said to be twenty cycles per second, written as 20 cps. The unit of frequency is Hertz (Hz) where 1 Hz is equivalent to 1 cycle/second. A frequency of 20 cps is represented as a frequency of 20 Hertz.

## Sound Waves

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This wave is discovered in 1654 by Otto Von Guericke. Sound is a vibration that propagates as an audible mechanical wave of pressure and displacement, through back and forth vibration of particles with any medium such as air, and water. If a sound wave is moving from left to right through air, then particles of air will be displaced both rightward and leftward as the energy of the sound wave passes through it. Sound Waves are the mechanical waves which can cause the sensation of hearing. These waves are produced by bodies vibrating at frequencies lying between the range of 20Hz and 20,000Hz perceived by the human ear. Ordinarily, we hear sound transmitted through the air. Unlike light, Sound cannot pass through vacuum.

## Standing Waves

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Stationary or standing waves are formed in a medium when two waves having equal amplitude and frequency moving in opposite directions along the same line, interfere in a confined space. In other words, it is a combination of two waves moving in opposite directions, each having the same amplitude and frequency. Example: A phone cord begins at the base and ends at the handset or is it the other way around. Generally, such waves are formed by the superposition of a forward wave and the reflected wave. Both longitudinal and transverse types of waves can form a stationary wave.

## Wave Theory

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According to the Wave theory all the particles exhibit both wave as well as particle nature. It basically describes light. Advances have been made by many scientists but the most significant was made by Maxwell. The conclusion was that the electromagnetic waves like visible light and ultraviolet light etc. had different frequency.
The photoelectric effect, Heisenberg principle of uncertainty, the concept of quantum or packet of light and the wave nature are all the part of the developments in wave theory.

## Types of Waves

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Waves come in many shapes and forms. While all waves share some basic characteristic properties and behaviors, some waves can be distinguished from others based on some characteristics. And one such method of differentiating it is by the means of the medium in which they travel. Waves can be classified into:
1) Electromagnetic Waves
2) Mechanical Waves
3) Matter Waves

## Wave Function

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The Wave function plays a significant role in quantum mechanics. It is called the probability amplitude in this field.
Features:
1. It gives us a probability of finding a particle in a given space.
2. It describes the state called quantum state for a particle.
3. It also describes the behavior of the particle.
4. It has complex number as its value.
For one particle it is a function of time and space. It is called psi and symbol is $\psi$.

## Electromagnetic Waves

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Electromagnetic waves are waves that have no medium to travel. It is a wave that is capable of transmitting its energy through an empty space or vacuum. Electromagnetic waves are caused because of the varying magnetic and electric fields. The existence of material medium is not essential for propagation. Electromagnetic waves are produced by the vibration of charged particles. They consist of periodic variations of electric and magnetic fields at right angles to each other and also at right angles to the direction of propagation. They are all the same kind of wavy disturbance that repeats itself over a distance called the wavelength. Electromagnetic waves that are produced on the sun subsequently travel to Earth through the vacuum of outer space.
Example: Light waves, radio waves, micro waves, X rays, TV transmissions

## Mechanical Waves

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Mechanical wave is a wave that is not capable of transmitting its energy through a vacuum. They are transmitted by both intermolecular forces and by collisions between the molecules. A Mechanical wave is a periodic disturbance, which requires a material medium (solid, liquid or gas) for its propagation. Energy and momentum propagates by motion of particles of medium but medium remains at previous position. The energy propagation in which disturbance propagates with definite velocity without changing its form is called Mechanical Wave. These waves are also known as elastic waves because their propagation depends upon the elastic properties of the medium through which they pass. In these waves, the particles of the medium just vibrate to and fro about their mean position.
Examples of Mechanical Waves are: Sound waves, water waves, ocean waves, vibration of string, earthquake waves, ultra sounds, vibrations in gas, and oscillations in spring, internal water waves, and waves in slink etc.

Waves traveling through a solid medium can either be transverse waves or longitudinal waves. Further, Mechanical waves can be classified into two types:
o Transverse waves
o Longitudinal Waves
o Surface Waves

The medium must possess the following properties for the propagation of the waves:
1) The medium should be able to return to its original condition after being disturbed, i.e., the medium must possess elasticity.
2) The medium must be capable of storing energy.
3) The frictional resistance must be negligible, so as not to damp the oscillatory movement.

These are the waves observed in the electrons and particles. The concept of water waves or de-Broglie waves explain about any aspect of the behavior or properties of a material object that varies in time or space in conformity with the mathematical equations that describe waves.

 More topics in Waves Properties of Waves Types of Waves Wave Frequency Period of a Wave Amplitude of a Wave Wave Speed Wavelength Wave Energy Electromagnetic Waves Modulation Frequency, Wavelength and Energy Acoustic Principles Basic Properties of Waves Oscillations and Waves Waves and Optics Superposition Direct Sensing Remote Sensing
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