Physics
Waves Physics
Waves in physics refer to the transfer of energy through a medium or space. They can be categorized as mechanical waves, which require a medium to propagate, or electromagnetic waves, which can travel through a vacuum. Waves exhibit properties such as amplitude, frequency, wavelength, and speed, and they play a fundamental role in various natural phenomena and technological applications.
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11 Key excerpts on "Waves Physics"
eBook - PDFWaves and Oscillations in Nature
An Introduction
- A Satya Narayanan, Swapan K Saha(Authors)
- 2015(Publication Date)
- CRC Press(Publisher)
1.2 What Is a Wave? A wave may be described as a periodic disturbance that transports energy from one point to another. Its direction of propagation is the direction in which energy is carried. It is thought to be the result of correlated oscillations occurring at every point along the path of the wave. The direction of these oscillations determines the nature of a particular wave, for example, 1. Transverse wave: The oscillations are known as transverse when the vibration takes place in a direction perpendicular to the direction of propagation. 2. Longitudinal wave: In this case, the vibrations are in the direction of propagation. For a sound wave, in which the pattern of disturbance caused by the movement of energy traveling through a medium as it propagates away from the source, the particles move back and forth parallel to the direction of the propagation of the wave. The wave phenomena and their oscillatory motion possess many degrees of freedom. They are the most important physical feature of a given system. Systems that are much larger than the atomic scales are continuous at scales of small distances. The discrete atomic properties tend to be replaced by their continuous local averages. Their degrees of freedom are denoted by a function of space and time. The infinite continuous set of degrees of freedom is subjected to a set of mutually dependent nonlinear equations of motion. These equations are fused into a partial differential equation, whose temporal dependence and derivatives are inherited from the Newtonian single atom equation of motion or its relativistic generalization. The spatial dependence and derivatives of this equation are byproducts of the discrete atomic indices in the continuum limit. A plane wave may be a simple two-dimensional (2D) or three-dimensional (3D) wave. Its characteristic is that all the points on a plane that is per-pendicular to the direction of propagation have the same phase value.
eBook - PDFPhysical Optics
Principles and Practices
- Abdul Al-Azzawi(Author)
- 2018(Publication Date)
- CRC Press(Publisher)
1 Waves 1.1 INTRODUCTION Light acts as a stream of particles that allow the light to transfer from one point to another. The coming chapters will deal with light as a wave. The purpose of this chapter is to explain the basic principles of light when transmitted, reflected, or refracted through an optical material as a wave. Energy can be transmitted from one place to another by vibrating objects, such as water waves that travel hundreds of kilometres over the ocean. The water particles move up and down as the wave passes. Similarly, when you shake a spiral spring, your energy is transferred from coil to coil down the spring. A wave is a transfer of energy in the form of vibrating particles in a medium. We live in a world surrounded by waves; some are visible and others are not. Water waves and the waves generated by a rope or a spring can be seen. Sound waves and radio waves cannot be seen. Waves also occur in light, sound, heat, microwaves, and in the ultra-microscopic world of atoms. Several types of waves and their applications will be presented in this chapter. Also in this chapter, along with the theoretical presentation, three experimental cases demonstrate the principles of Hook’s law, wave generation, and the simple pendulum. 1.2 THE NATURE OF WAVES 1.2.1 E NERGY T RANSFER There are various ways in which energy can be transferred from one place to another. The flow of heat through a metal from a region of high temperature to one of low temperature represents one method of transferring energy. The flow of electricity through a metal is somewhat analogous to heat flow. The conduction of heat energy and electric energy through metals depends upon the motion of particles that compose the metal. 1 The transfer of energy by the gross movement of materials or objects from one place to another is the basic principle of the nature of waves. Winds, tides, and projectiles in flight are examples for this type.
eBook - PDF- 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.
eBook - PDFLet 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)
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. We have learned to produce electromagnetic waves and to put them to a variety of uses, many of which are now taken almost for granted. Radio waves facilitate the remote communi-cation that enables us to hear and to see the latest news and to watch our favourite television programmes. We can receive information about the lunar surface from space probes. In med-icine, lasers produce waves for keyhole surgery; X-rays are used in diagnostic imaging and radiation therapy; infrared waves heat muscles and relieve pain. Microwaves cook food; radar waves guide planes and ships. Last but not least, a tiny infrared beam from our remote control allows us to change channels without leaving our armchair in front of the TV set! Waves on a sandy beach at Cabo Polonio, Uruguay. Courtesy of Johntex, 2006 . Introducing Waves 151 Once we become aware of the seemingly endless variety of waves, it begs questions such as: Do all waves have something in common? How can we deal with waves mathematically? What is the justification to say that light behaves as a wave? Mechanical waves in a medium When a medium is disturbed by a wave, individual particles oscillate about their equilibrium positions and transmit energy by their mutual interactions. A stone dropped into the middle of a pond gives rise to waves spreading out on the surface of the water in ever-increasing circles. The expanding waves show that something definitely propagates, but it is not the water itself; ducks sitting in the path of the wave bob up and down but do not necessarily move in the apparent direction of propagation.
eBook - PDFOcean 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.
eBook - PDFFrom Atoms to Galaxies
A Conceptual Physics Approach to Scientific Awareness
- Sadri Hassani(Author)
- 2010(Publication Date)
- CRC Press(Publisher)
Superposition The property of waves whereby two waves reaching a single point add to give the oscillation of the medium at that point. Transverse Wave A wave for which the medium oscillates perpendicular to the direction of wave motion. Wave A continuous succession of pulses traveling in a medium. Wavelength The distance between two successive similar points of a wave. Denoted by λ , wavelength is measured in meters. 172 Chapter 11 Waves 11.5.3 Review Questions 11.1. Who thought that light was composed of particles? Who thought that light was a wave? 11.2. What is a mechanical wave? How does it arise? Give an example of a mechanical wave. 11.3. What is oscillation? Give an example of a simple harmonic motion (SHM). What do we call a system which performs SHM? 11.4. Define period, cycle, and frequency and state what relation exists between period and frequency. 11.5. What is a pulse? What is a wave as defined in terms of pulses? What is a simple harmonic wave? State how you can produce a simple harmonic wave. 11.6. Define wavelength. How is it related to the period of a wave? 11.7. As you watch a wave on a rope, you notice a motion along the rope. Is it the rope that is moving? Explain! 11.8. What familiar property of sound is described by frequency? What familiar property of light is described by frequency? 11.9. What is the range of audible sound frequencies? What is the range of visible light wavelengths? 11.10. What physical property of a wave is associated with its energy (or intensity)? 11.11. What is a transverse wave? What is a longitudinal wave? Which one has polariza-tion property? 11.12. What is constructive interference? What is destructive interference? Enumerate all conditions required of two sources to produce interference. Does any double-slit meet these conditions? Explain! 11.13. What is diffraction? Why do we expect diffraction based on multiple-slit interfer-ence? Enumerate all conditions required of an aperture to produce diffraction.
eBook - PDF- David J. Griffiths(Author)
- 2017(Publication Date)
- Cambridge University Press(Publisher)
C H A P T E R 9 Electromagnetic Waves 9.1 WAVES IN ONE DIMENSION 9.1.1 The Wave Equation What is a “wave”? I don’t think I can give you an entirely satisfactory answer—the concept is intrinsically somewhat vague—but here’s a start: A wave is a distur- bance of a continuous medium that propagates with a fixed shape at constant ve- locity. Immediately I must add qualifiers: In the presence of absorption, the wave will diminish in size as it moves; if the medium is dispersive, different frequencies travel at different speeds; in two or three dimensions, as the wave spreads out, its amplitude will decrease; and of course standing waves don’t propagate at all. But these are refinements; let’s start with the simple case: fixed shape, constant speed (Fig. 9.1). How would you represent such an object mathematically? In the figure, I have drawn the wave at two different times, once at t = 0, and again at some later time t —each point on the wave form simply shifts to the right by an amount vt , where v is the velocity. Maybe the wave is generated by shaking one end of a taut string; f (z , t ) represents the displacement of the string at the point z , at time t . Given the initial shape of the string, g(z ) ≡ f (z , 0), what is the subsequent form, f (z , t )? Well, the displacement at point z , at the later time t , is the same as the displacement a distance vt to the left (i.e. at z − vt ), back at time t = 0: f (z , t ) = f (z − vt , 0) = g(z − vt ). (9.1) That statement captures (mathematically) the essence of wave motion. It tells us that the function f (z , t ), which might have depended on z and t in any old way, in fact depends on them only in the very special combination z − vt ; when that vt f v z f(z, 0) f(z, t) FIGURE 9.1 382 9.1 Waves in One Dimension 383 θ′ z z T T f z + Δz θ FIGURE 9.2 is true, the function f (z , t ) represents a wave of fixed shape traveling in the z direction at speed v.
eBook - PDF- Lincoln Wolfenstein, Joao P. Silva(Authors)
- 2010(Publication Date)
- CRC Press(Publisher)
11 2 C H A P T E R Waves That Are Particles; Particles That Are Waves A major revolution in our understanding of nature took place in the early twentieth century; we learned that light can have particle-like properties and that particles can have wave-like properties. This is deeply ingrained into the standard model of particle physics. 2.1 PARTICLES VERSUS WAVES This book tells the exhilarating recent history of the search for the funda-mental building blocks of all things and their interactions. When physi-cists mention “point particles,” they may not be talking about fundamental particles at all. Point particles might have some internal structure, but they are so named because, whatever their internal structure might be, it has no bearing on the phenomenon under study. For example, consider a rigid ball sliding down an inclined plane without rolling and without friction. If this experiment is performed in a vacuum (that is, with all the air sucked out), the velocity that the ball has after it slides for 1 in. can be calculated ignoring what the ball is made of. It is even independent of the ball’s mass; it depends exclusively on the slope of the inclined plane. There is an interesting way to describe how this happens. When the ball is placed in a high position, we say that it has the potential to gain speed and we ascribe to it some potential energy. As it accelerates down the 12 ◾ Exploring Fundamental Particles inclined plane, we say that it transforms this potential energy into kinetic energy, from the Greek word kinesis , which means motion. That is, the potential energy the ball had because it was placed in a high position is transformed into the kinetic energy associated with its speed as it moves down the plane. 1 Another interesting quantity is the momentum of this particle. Momentum is an arrow (so-called vector) that has a size equal to the prod-uct of mass with velocity, and it has the direction of the particle’s movement.
eBook - PDF- John Kimball(Author)
- 2015(Publication Date)
- CRC Press(Publisher)
147 5 W AVES 5.1 Introduction Waves are everywhere. Sound waves, radio waves, and light waves are as much a part of the world we know as solids, liquids, and gasses. After an overview of general wave properties with some examples, the descriptions emphasize sound and light waves because without these waves we would be lost. Two of our five senses, vision and hearing, interpret light and sound waves and tell us almost every-thing we know. 5.2 Common Features of Waves The geometries of sound and light waves are suggested by the water waves (gravity waves) that can be seen on the surface of a lake or a bathtub. But, the analogy should be approached with caution. In many ways, sound and light are simpler than both water waves and the wave function of quantum mechanics (Chapter 6). The water waves in Figure 5.1 spread out in circles. A long way from the center, the wave peaks and valleys are nearly straight lines. The waves become nearly “plane waves” with a shape that varies only in the direction pointed away from the wave source. Far from the source, light and sound waves also approach plane wave shape. 5.2.1 Wavelength, Frequency, Speed, Amplitude, and Energy The simplest wave geometry is the plane wave. The simplest plane wave shape is the “sine wave” shown in Figure 5.2. Any wave shape can be constructed by adding together various sine waves, so the sine wave building blocks of all waves deserve special attention. 148 PHYSICS CURIOSITIES, ODDITIES, AND NOVELTIES Sine waves are characterized by three quantities: wavelength, fre-quency, and amplitude. The wavelength is the distance between wave peaks. The frequency is the number of times a wave oscillates up and down each second. The amplitude is the height of the wave. The speed of a wave is the distance one of the wave peaks moves in 1 second. It is related to wavelength and frequency by an impor-tant equation.
eBook - PDFPhysics at a Glance
Full Physics Content of the New GCSE
- Tim Mills(Author)
- 2008(Publication Date)
- CRC Press(Publisher)
28 Questions 1. Identify the measurements a, b and c in the following diagrams: 2. Write a sentence to define each of the following terms: a. Wavelength. b. Frequency. c. Amplitude. 2. Give one similarity and one difference between a longitudinal and transverse wave and give an example of each. 3. For each of particles a, b, and c in the diagram decide if the particle is moving up, moving down, or is momentarily stationary. A wave is a periodic disturbance of a medium. TRANSFER OF ENERGY WAVES Describing Waves All waves transfer energy from one place to another, without transferring any matter. Speed = distance travelled by a wave crest or compression in one second. The direction of wave motion is defined as the direction energy is transferred. Frequency is the number of waves per second produced by the source that pass through a given point in the medium. Measured in waves per second or Hertz, Hz. The particles of the medium oscillate about fixed positions along the same line as the wave energy travels. Wave direction Particles of the medium oscillate about fixed positions at right angles to the direction of wave travel. Wavelength ( λ ) – distance between the same point on two adjacent disturbances. Measured in metres. Amplitude – distance between a crest or trough and the undisturbed position . Trough All particles moving down Examples longitudinal: • Sound Particles spread out – rarefaction Particles close – compression Shows direction of energy transfer Examples transverse: • Surface water waves • Light • Plucked guitar string Wavefront Ray at right angles to wavefront Particles oscillating up and down Wave direction Crest (peak) All particles moving up λ λ λ The medium is the material that is disturbed as the wave passes through it. W A V E S T w o t y p e s T r a n s v e r s e w a v e s L o n g i t u d i n a l w a v e s Particles oscillating side to side Compression Rarefaction a b Position along wave c a b c Wave direction
No longer available |Learn more- (Author)
- 2014(Publication Date)
- Learning Press(Publisher)
Water waves are periodic variations in the height of a body of water. In a crystal lattice vibration, atomic positions vary periodically in both lattice position and time. Wavelength is a measure of the distance between repetitions of a shape feature such as peaks, valleys, or zero-crossings, not a measure of how far any given particle moves. For example, in waves over deep water a particle in the water moves in a circle of the same diameter as the wave height, unrelated to wavelength. Sinusoidal waves In linear media, any wave pattern can be described in terms of the independent pro-pagation of sinusoidal components. The wavelength λ of a sinusoidal waveform traveling at constant speed v is given by: Refraction: when a plane wave encounters a medium in which it has a slower speed, the wavelength decreases, and the direction adjusts accordingly. ________________________ WORLD TECHNOLOGIES ________________________ where v is called the phase speed (magnitude of the phase velocity) of the wave and f is the wave's frequency. In the case of electromagnetic radiation—such as light—in free space, the phase speed is the speed of light, about 3×10 8 m/s. For sound waves in air, the speed of sound is 343 m/s (1238 km/h) (at room temperature and atmospheric pressure). As an example, the wave-length of a 100 MHz electromagnetic (radio) wave is about: 3×10 8 m/s divided by 100×10 6 Hz = 3 metres. Visible light ranges from deep red, roughly 700 nm, to violet, roughly 400 nm (430–750 THz). The wavelengths of sound frequencies audible to the human ear (20 Hz–20 kHz) are between approximately 17 m and 17 mm, respectively, assuming a typical speed of sound of about 343 m/s; the wavelengths in audible sound are much longer than those in visible light. Frequency and wavelength can change independently, but only when the speed of the wave changes.
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