Waves in Communication

9 Key excerpts on "Waves in Communication"

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  Let There Be Light: The Story Of Light From Atoms To Galaxies (2nd Edition)

  The Story of Light from Atoms to Galaxies

  • Alex Montwill, Ann Breslin(Authors)
  • 2013(Publication Date)
  • ICP

    (Publisher)

  Chapter 6 Introducing Waves What is a wave? Waves are so diverse that we might tend to regard different types of waves as separate entities, unrelated to one another. Do events such as the devastation of a region by an earthquake and the melodic tones of a musical instrument have anything in common? In this chapter we explore the com-mon ground between these and many other phenomena. Waves carry energy from one place to another. They also act as messengers, transmitting information. We look at different types of waves, how they are created, what they are ‘made of ’ and how they carry out their functions of carrier and messenger. To deal with some aspects of wave behaviour, we need to express the properties of the waves mathematically. We can then make quantitative predictions regarding many wave-related phe-nomena seen in nature. In a mathematical analysis of waves, it is most convenient to use the simplest type of wave form — a continuous sine wave. It is gratifying, if rather startling, to find that even the most complicated periodic waves can be constructed simply by adding a number of these sine waves. 6.1 Waves — the basic means of communication When talking about waves , we most likely picture a seaside scene with ocean waves approaching the shore or perhaps a ship at sea tossed in a storm. A survey asking the question ‘What serves as the most common means of communication?’ would be unlikely to favour the answer ‘ Waves ’. Yet, heat and light from 149 150 Let There Be Light 2nd Edition the sun are carried by waves. We could neither see nor speak to one another were it not for light waves and sound waves. Even the sensation of touch relies on the transmission of nerve impulses, which are composed of wave packets. Electromagnetic waves, which pervade all space, and with-out which the universe could not exist, are the basic theme of this book. Light is just one member of that family. These waves propagate in a mysterious way, as we shall see in later chapters.

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  Let There Be Light

  The Story of Light from Atoms to Galaxies

  • Ann Breslin, Alex Montwill(Authors)
  • 2013(Publication Date)
  • ICP

    (Publisher)

  Chapter 6

  Introducing Waves

  What is a wave? Waves are so diverse that we might tend to regard different types of waves as separate entities, unrelated to one another. Do events such as the devastation of a region by an earthquake and the melodic tones of a musical instrument have anything in common? In this chapter we explore the common ground between these and many other phenomena.

  Waves carry energy from one place to another. They also act as messengers, transmitting information. We look at different types of waves, how they are created, what they are ‘made of’ and how they carry out their functions of carrier and messenger.

  To deal with some aspects of wave behaviour, we need to express the properties of the waves mathematically. We can then make quantitative predictions regarding many wave-related phenomena seen in nature. In a mathematical analysis of waves, it is most convenient to use the simplest type of wave form — a continuous sine wave. It is gratifying, if rather startling, to find that even the most complicated periodic waves can be constructed simply by adding a number of these sine waves.

  6.1 Waves — the basic means of communication

  When talking about waves, we most likely picture a seaside scene with ocean waves approaching the shore or perhaps a ship at sea tossed in a storm. A survey asking the question ‘What serves as the most common means of communication?’ would be unlikely to favour the answer ‘Waves’. Yet, heat and light from the sun are carried by waves. We could neither see nor speak to one another were it not for light waves and sound waves. Even the sensation of touch relies on the transmission of nerve impulses, which are composed of wave packets.

  Waves on a sandy beach at Cabo Polonio, Uruguay. Courtesy of Johntex, 2006.

  Electromagnetic waves, which pervade all space, and without which the universe could not exist, are the basic theme of this book. Light

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  Wireless Sensors and Instruments

  Networks, Design, and Applications

  • Halit Eren(Author)
  • 2018(Publication Date)
  • CRC Press

    (Publisher)

  2

  Wireless Communication

  ______________

  Communication is the transfer of information from one device to another. Modern communication systems involve man-made signals that can be transmitted to different places. The communication signals that carry the information can be in the form of electrical energy, such as currents and voltages, electromagnetic energy, optical energy, or sonic energy. Signals are generated electronically and transmitted via cables and wired lines or wire-lessly through electromagnetic radiation in space in the form of radio waves or microwave energy. Signals can also be transmitted by optical or sonic methods.

  Communication between instruments takes place via transmission of electrical signals from a source to a sink. The originator of the information is called the source, and the receiving end is the sink. The source converts the original message (e.g., voice, text) into electrical signals that are transmitted to the sink. The source also produces electrical signals suitable for transmission in the selected media—wired, wireless, optical, and so on. The hardware and software that comprises the source is called the transmitter. The task of the transmitter is to process the communication signal into a suitable form for successful transmission along a selected channel. The communication channel is the medium that connects the transmitter to the receiver. The medium can be wires, coaxial cables, fiber-optic cables, or space that carries electromagnetic waves or light waves. On the sink side, a receiver extracts the signal coming from the communication channel and processes it such that the information can be interpreted and understood. The sink converts the electrical signal from the receiver back into the form of the original information, such as voice, text, or data.

  This chapter concentrates on the basic principles of wireless communication techniques using electromagnetic waves, particularly at radio frequencies. Wireless communication techniques are being used in a wide range of applications from industrial systems to a variety of consumer products.

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  Electricity and Electronics Fundamentals, Second Edition

  • Dale R. Patrick, Stephen W. Fardo(Authors)
  • 2020(Publication Date)
  • River Publishers

    (Publisher)

  Chapter 7 Electronic Communications INTRODUCTION Sound is made louder by using electronic amplifi- ers. High-level sound amplification made it possible to communicate over a rather substantial distance. A pub- lic address amplifier system, for example, permits an an- nouncer to communicate with a large number of people in a stadium or an arena. Even the most sophisticated sound system, however, has some limitations. Sound waves moving away from the source have a tendency to become somewhat weaker the farther they travel. An in- crease in signal strength does not, therefore, necessarily solve this problem. People near large speakers usually become uncomfortable when the sound is increased to a high level. It is possible, however, to communicate with people over long distances without increasing sound lev- els. Electromagnetic waves make this type of communica- tion possible. Radio, television, long-distance telephone, and cellular phone communication are achieved by this process. Electromagnetic wave communications systems play an important role in our daily lives. We listen to ra- dio receivers, watch television, talk to friends on cellular telephones, and even communicate with astronauts by electromagnetic waves. Because this type of communica- tion is widely used today, it is important that we have some basic understanding of it. In this chapter we investigate how sound is trans- mitted through the air by electromagnetic waves. This type of communication uses high-frequency alternating current or radio frequency energy for its operation. These signals travel through the air at 186,000 miles per second. Electromagnetic communication permits sound to travel long distances al-most instantaneously. OBJECTIVES Upon completion of this chapter, you will be able to: 1. Explain the advantages, disadvantages, and char- acteristics of amplitude modulation and frequency modulation.

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  Mathematics of Wave Propagation

  • Julian L. Davis(Author)
  • 2021(Publication Date)
  • Princeton University Press

    (Publisher)

  C H A P T E R O N E Physics of Propagating Waves INTRODUCTION In this chapter we shall discuss the physics of propagating waves, starting with simple physical models and then giving an elementary combined physical and mathematical treatment of waves traveling in continuous media. A mathematical treatment is reserved for subsequent chapters. For our purposes a continuous medium is one in which there is a continuous distribution of matter in the sense that a differential volume of material (in the mathematical sense) has the same properties as the material in the large. This means that molecular and crystalline struc-tures are neglected. It is known that electromagnetic (EM) waves travel in a vacuum with the speed of light. (A vacuum is a continuous medium with zero density of matter.) A propagating medium involves oscillations of the material through which the wave travels, with a wave velocity characteristic of the material and the temperature. For example, sound waves travel with a wave velocity that depends on the temperature and the density of the medium (air or fluid). For EM waves traveling in a vacuum, we have an oscillating electric intensity vector and an oscillating magnetic intensity vector normal to the electric vector. DISCRETE WAVE-PROPAGATING SYSTEMS Although the main thrust of this book is a treatment of waves traveling in continuous media, it is useful to construct a physical model composed of a discrete set of oscillating masses coupled by springs. We shall neglect friction. The limit as the number of masses and springs becomes infinite in a finite region yields a continuous medium. The simplest oscillating system consists of a spring fixed at one end and coupled to a mass. The small-amplitude oscillations of the mass

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  Ocean Waves and Oscillating Systems: Volume 8

  Linear Interactions Including Wave-Energy Extraction

  • Johannes Falnes, Adi Kurniawan(Authors)
  • 2020(Publication Date)
  • Cambridge University Press

    (Publisher)

  CHAPTER THREE Interaction between Oscillations and Waves There are many different types of waves in nature. Apart from the visible waves on the surface of oceans and lakes, there are, for instance, sound waves, light waves and other electromagnetic waves. This chapter gives a brief description of waves in general and compares surface waves on water with other types of waves. It also presents a simple generic discussion on the interaction between waves and oscillations. One phenomenon is generated waves radiated from an oscillator, and another phenomenon is oscillations excited by a wave incident upon the oscillating system. We shall define the radiation resistance in terms of the power associated with the wave generated by the oscillator. The ‘added mass’ is related to added energy associated with the wave-generating process, not to kinetic energy alone but to the difference between kinetic and potential energies. 3.1 Comparison of Waves on Water with Other Waves Waves on water propagate along a surface. Acoustic waves in a fluid and elec- tromagnetic waves in free space may propagate in any direction in a three- dimensional space. Waves on a stretched string propagate along a line (in a one-dimensional ‘space’). The same may be said about waves on water in a canal and about guided acoustic waves or guided electromagnetic waves along cylindrical structures, although in these cases the physical quantities (pressure, velocity, electric field, magnetic field, etc.) may vary in directions transverse to the direction of wave propagation. As was mentioned in Chapter 2, there is an exchange of kinetic energy and potential energy in a mechanical oscillator (or magnetic energy and electric energy in the electric analogue). In a propagating wave, too, there is interaction between different forms of energy—for instance, magnetic and electric energy with electromagnetic waves, and kinetic and potential energy with mechani- cal waves, such as acoustic waves and water waves.

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  Principles of Physical Optics

  • Charles A. Bennett(Author)
  • 2022(Publication Date)
  • Wiley

    (Publisher)

  1 1 The Physics of Waves The solution of the difficulty is that the two mental pictures which experiment lead us to form — the one of the particles, the other of the waves — are both incomplete and have only the validity of analogies which are accurate only in limiting cases. Heisenberg 1.1 Introduction The properties of waves are central to the study of optics. As we will see, light (or more prop- erly, electromagnetic radiation) has both particle and wave properties. These complementary aspects are a result of quantum mechanics, and prior to the early 1900s, there were two schools of thought. Newton postulated that light consists of particles, while contemporaries Huygens and Hooke promoted a wave theory of light. The matter seemed settled with Young’s important double-slit experiment offering clear experimental evidence that light is a wave. Maxwell’s sweeping theory of electromagnetism finally provided a deep and complete description of electromagnetic waves that we consider in detail in Chapter 2. Although current theories of optics include both wave and particle descriptions, the wave picture still forms the bedrock of most optical technology. In this chapter, we will outline some general properties that apply to traveling waves of all types. 1.2 One-Dimensional Wave Equation Mechanical waves travel within elastic media whose material properties provide restoring forces that result in oscillation. When a guitar string is plucked, it is displaced away from its equilibrium position, and the mechanical energy of this disturbance subsequently propagates along the string as traveling waves. In this case, the waves are transverse, meaning that the displacement of the medium (the string) is perpendicular to the direction of energy travel. Acoustic waves in a gas are longitudinal, meaning that the gas molecules are displaced back and forth along the direction of energy flow as regions of high and low pressure are created along the wave.

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  The Handy Physics Answer Book

  • Charles Liu(Author)
  • 2020(Publication Date)
  • Visible Ink Press

    (Publisher)

  WAVES

  What is a wave?

  A wave is a traveling disturbance that moves energy from one location to another without transferring matter. Oscillations in a medium or material create mechanical waves that propagate away from the location of the oscillation. For example, a pebble dropped into a pool of water creates vertical oscillations in the water, while the wave propagates outward horizontally along the surface of the water.

  What are the two main forms of waves?

  Transverse waves and longitudinal waves are the two major forms of waves.

  In a transverse wave, the wave itself and its energy move away from the source perpendicular to the direction of the oscillations. A transverse wave can be created, for example, by repeatedly shaking a string or rope up and down. The string moves up (the highest point is called the “crest”) and down (the lowest point is called the “trough”) while the wave travels.

  The oscillations in longitudinal waves move in the same direction that the wave is moving. A longitudinal wave can be created, for example, by repeatedly pushing and pulling on a long, soft spring.

  Can the two main forms of waves be combined?

  Yes, they often do combine. Ripples in a pond, for example, are a combination of transverse and longitudinal waves that can move outward in circles. As in the case of transverse and longitudinal waves alone, energy is transferred, but matter is not moved.

  What determines the velocity of a wave?

  The velocity of a wave depends upon the material or medium in which it is traveling. Typically, the stronger the coupling between the atoms or molecules that make up the medium and the less massive they are, the faster the wave will travel. All waves of the same type (transverse or longitudinal) travel at the same speed through the same medium. For example, a sound wave in air at 0°C will travel at 331 meters per second regardless of the sound’s frequency or amplitude.

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  Principles of Engineering Physics 1

  • Md Nazoor Khan, Simanchala Panigrahi(Authors)
  • 2017(Publication Date)
  • Cambridge University Press

    (Publisher)

  2 The waves move with a velocity depending upon the properties of the medium. The waves remain stationary and do not move. 3 Each particle of the medium executes periodic motion about their mean position with the same amplitude. Except the node, all the particles of the medium execute SHO with varying amplitude. 4 There is a continuous change of phase from particle to particle. All the particles between two consecutive nodes are at the same phase, but differ in phase by p from those in the preceding as well as succeeding similar segments. 5 At any instant all the particles do not come together in the mean position, they pass their mean position in succession but with the same velocity. All the particles pass their mean position at a time, but with different velocities. Oscillations and Waves 57 6 Each particle of the medium undergoes similar change of pressure and density There is no change of pressure and densities at the antinodes while there is maximum change of pressure and densities at the nodes. 7 There is transmission of energy across every plane in the direction of propagation of waves. There is no flow of energy across any plane. 8 A complete wavelength contains a compression and rarefaction in the case of longitudinal waves and crest and trough in the case of transverse waves. The wavelength is the distance between two alternate nodes and anti nodes. 9 Compression and rarefaction move from point to point throughout the medium. The compression and rarefaction do not move from point to point; they simply appear at and disappear at certain equidistance fixed points. 10 No particle of the medium is permanently at rest.

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