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Waves

When a pebble is through in water of the pond then it creates a disturbance and forms ripples which travel in the direction of the other end of the pond. These are waves in medium water. The wave is defined as the energy transfer through medium with regular vibration or oscillating motion. Many processes are related to transferring of energy in the form of material through the medium.

Waves

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.

 

Wave Definition

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A disturbance causing energy transfer from one point to another without the actual movement of particle is called a wave.

There are two modes of energy transfer :
  1. Particle motion
  2. wave motion

When no particle is transferred from one part of space to other although energy is transferred then we call it wave or simply wave.
Wave

The disturbance can be by natural reasons like air, wind, storm etc or it can be caused intentionally.
A wave can be of many times like transverse wave and longitudinal wave etc. 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 : The movement of the wave is mostly rectilinear or in a straight line. It can travel through various medium like gas, liquid etc. a medium can be a bounded medium, a linear medium, an uniform medium, an isotropic and an anisotropic medium. These are also called as the transmission medium.

It under goes 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 angle of reflection.
  2. Interference: when waves of equal frequency and nearly equal amplitude are superimposed then the phenomenon of interference occurs. It can be of two types viz. constructive 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.
  6. Polarization: A wave oscillating in one plane or direction is called a polarized wave. It can be circular polarized or plane polarized. Even we can use the polarization filter for this purpose.
  7. 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.
The wave speed is the distance covered by the wave in the given interval of time.
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.
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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.
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Wave length is the Parts of a Wave, which 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.
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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 a Wave

Wave Height gives the amplitude of the wave. So, the greater the intensity of a sound, the greater will be the amplitude. It is the maximum positive displacement of the medium from its undisturbed position to the top of a crest.
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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

This is the number of waves that pass a point in each second. This  Parts 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 . A frequency of 20 cps is noted as a frequency of 20 Hertz.
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This wave is discovered in 1654 by Otto Von Guericke. These 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.
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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.
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.
Waves can be classified in two types:
  1. Electromagnetic Waves
  2. Mechanical waves
  3. Matter waves


Electromagnetic wave:

The existence of medium is not essential for propagation. The Periodic changes takes place in electric and magnetic fields hence it is called Electromagnetic wave.        
 

Mechanical wave: 

The existence of medium is essential for propagation. The energy propagation in which disturbance propagates with definite velocity without changing its form is called Mechanical wave. Energy and momentum propagates by motion of particles of medium. But medium remains at previous position. The mass transfer does not take place.
Propagation is possible due to property of medium viz. elasticity and inertia.
 
Mechanical waves can be of two types :
  1. Transverse waves
  2. Longitudinal Waves

Examples: vibration of string, vibration of string, the surface wave produced on the surface of solid and liquid, sound waves, tsunami waves, earthquake P waves, ultra sounds, vibrations in gas, and oscillations in spring, internal water waves, and waves in slink etc.

Matter Waves:

These are the waves observed in the electrons and particles. The De-broglie waves explains a lot about this.
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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 are waves that can pass through vacuum in addition to passing through matter. In other words, a material medium is not necessary for their propagation. 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.
Example: Light waves, radio waves, micro waves, x-rays.
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Mechanical Waves

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A Mechanical wave is a periodic disturbance, which requires a material medium (solid, liquid or gas) for its propagation. These waves are also known as elastic waves because their propagation depends upon the elastic properties of the medium through which they pass.

Examples for Mechanical waves are:

Sound waves and water waves, vibration of string, the surface wave produced on the surface of solid and liquid, sound waves, tsunami waves, earthquake P waves, ultra sounds, vibrations in gas, and oscillations in spring, internal water waves, and waves in slink etc.
In these waves, the particles of the medium just vibrate to and fro about their mean position.

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.     
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
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