Applications of Waves
Applications of waves in physics include communication technologies such as radio, television, and cell phones, which rely on the transmission of electromagnetic waves. Additionally, medical imaging techniques like ultrasound and MRI utilize the properties of waves to create detailed images of the human body. Industrial applications also use waves for non-destructive testing and materials processing.
4 Key excerpts on "Applications of Waves"
eBook - ePub- David M. Scott(Author)
- 2018(Publication Date)
- CRC Press(Publisher)
...3 Sound and Wave Phenomena 3.1 Sound Hearing is one of the five basic senses, and sound therefore has always been a means of gathering information about one’s immediate environment. For instance, an explorer who is looking for a stream naturally follows the sound of running water. Anyone who works with wood knows that it is usually possible to determine the quality of a board by tapping on it and listening to the sound. It should therefore come as no surprise that industrial sensors use sound to measure a variety of parameters such as distance, film thickness, particle size, and solids concentration. These applications will be discussed in later chapters; the purpose of this chapter is to review the properties of sound and to introduce concepts that will be used later. What we perceive as sound is a set of momentary fluctuations in local air pressure caused by a mechanical motion, such as the ringing of a bell (Figure 3.1). As the surface of the bell moves imperceptibly and rapidly, it pushes on the molecules in the air and sets a wave of alternating compression and rarefaction in motion. A wave is a disturbance that moves through a given medium or field, and in the case of Figure 3.1 the regions of compression (called the wave front) and rarefaction move to the right. The sound is heard when this wave exerts a varying pressure on the eardrum. These vibrations are carried to the inner ear, where they are sensed within the cochlea. In air, sound propagates as a longitudinal wave, which means that the air molecules oscillate back and forth along the direction of wave propagation. Figure 3.2 depicts the gas molecules in a hypothetical sound wave at five different moments in time as they move along the direction of propagation. The regions where the molecules are bunched together is a local high-pressure region, and the graph above each cartoon of the air molecules shows the local pressure P(x) as a function of position x...
eBook - ePubThe Quantum World
Quantum Physics for Everyone
- Kenneth W. Ford(Author)
- 2005(Publication Date)
- Harvard University Press(Publisher)
...Even with the sum-over-histories approach, concepts such as wavelength, diffraction, and interference show up.*So the answer to the question posed at the beginning of this section, “Are waves necessary?” is: “No, not really.” But what is going on mimics wave behavior so closely that one might as well use waves to describe reality.*The wave-particle duality led to a slew of Nobel Prizes: Einstein in 1921 for the photoelectric effect, Compton in 1927 for the “Compton effect” (photon scattering from electrons), de Broglie in 1929 for discovering the wave nature of electrons, Schrödinger in 1933 for “new forms of atomic theory” (his wave equation), Davisson and Thomson in 1937 for the diffraction of electrons by crystals, and Max Born in 1954 for relating the wave function to probability.*A water wave is called atransversewave because the water moves mainly up and down transverse to the direction of motion of the wave. Radio waves and light waves are also transverse. A sound wave is a longitudinal wave. This means that the vibrating material is moving back and forth parallel to the direction of wave motion. A longitudinal wave still has crests (locations of above-average density) and troughs (locations of below-average density), so it has a well-defined wavelength, as well as frequency and speed.*The rule that wave speed doesn’t depend on wave energy is precisely true for light waves and true to very good approximation for most other waves. Shock waves provide an exception to the rule. They are more energetic and move faster than ordinary sound waves.*The relativistic definition of momentum for a massless particle isp=E/c, whereEis the particle’s energy and c is the speed of light.*The historians of science Gerald Holton and Stephen Brush have remarked that the particle theory of light was not as dogmatically entertained by Isaac Newton, its supposed champion, as by his later disciples...
eBook - ePubPrimer on Radiation Oncology Physics
Video Tutorials with Textbook and Problems
- Eric Ford(Author)
- 2020(Publication Date)
- CRC Press(Publisher)
...1 Basic Physics 1.1 Waves and Particles 1.1.1 Electromagnetic Waves Electromagnetic waves come in many forms, e.g. radio waves, lights, and X-rays. In 1870, James Clerk Maxwell developed a formalism to describe these electromagnetic waves in which the changing magnetic field creates an electric field and vice versa to form a self-sustaining wave that propagates at a speed given the symbol c, the speed of light, which is 3·10 8 m/s in a vacuum. Three properties describe waves: the speed, c, wavelength, λ, and frequency, ν (sometimes written as f). See Figure 1.1.1. These are related by FIGURE 1.1.1 Properties of electromagnetic waves. c = λ ⋅ ν (1.1) The units are c (m/s), λ (m), and frequency, ν (1/s given the special unit Hertz, Hz). The type of wave is determined by the wavelength (or equivalently the frequency), see Figure 1.1.1. Note that optical light occupies a relatively narrow range of the spectrum from 400 to 700 nanometers (nm). At very short wavelengths electromagnetic waves are X-rays. X-rays were first produced and characterized by Wilhelm Roentgen in 1895. They have a wavelength similar to the size of the atom itself. It is more common to describe these waves by their energy instead of their wavelength. The energy, E, is given by E = h ν (1.2) Here h is Planck’s constant, a fundamental constant of nature whose value is 6.626·10 −34 m 2 kg/s. A common unit for energy useful for medical physics applications is the electron-volt, eV, which is the energy gained by one electron moving through a potential of one volt. X-rays and particles in medical physics applications often have energies in keV to MeV range. 1.1.2 Particles The various particles of importance for medical physics applications are shown in Table 1.1 The electron was first discovered by J.J. Thompson in 1897. Somewhat later, in 1908, Robert A. Millikan and Harvey Fletcher performed a series of experiments which showed that the charge of the electron is quantized, i.e...
- Charles Elachi, Jakob J. van Zyl(Authors)
- 2021(Publication Date)
- Wiley(Publisher)
...2 Nature and Properties of Electromagnetic Waves 2.1 Fundamental Properties of Electromagnetic Waves Electromagnetic energy is the means by which information is transmitted from an object to the sensor. Information could be encoded in the frequency content, intensity, or polarization of the electromagnetic wave. The information is propagated by electromagnetic radiation at the velocity of light from the source directly through free space, or indirectly by reflection, scattering, and reradiation to the sensor. The interaction of electromagnetic waves with natural surfaces and atmospheres is strongly dependent on the frequency of the waves. Waves in different spectral bands tend to excite different interaction mechanisms such as electronic, molecular, or conductive mechanisms. 2.1.1 Electromagnetic Spectrum The electromagnetic spectrum is divided into a number of spectral regions. For the purpose of this text, we use the classification illustrated in Figure 2.1. The radio band covers the region of wavelengths longer than 10 cm (frequency less than 3 GHz). This region is used by active radio sensors such as imaging radars, altimeters, and sounders, and, to a lesser extent, passive radiometers. The microwave band covers the neighboring region, down to a wavelength of 1 mm (300 GHz frequency). In this region, most of the interactions are governed by molecular rotation, particularly at the shorter wavelengths. This region is mostly used by microwave radiometers/spectrometers and radar systems. The infrared band covers the spectral region from 1 mm to 0.7 μm. This region is sometimes subdivided into subregions called submillimeter, far infrared, thermal infrared, and near infrared. In this region, molecular rotation and vibration play an important role. Imagers, spectrometers, radiometers, polarimeters, and lasers are used in this region for remote sensing...
