1. Waves in essence

2018 ◽  
pp. 1-29
Author(s):  
Mike Goldsmith
Keyword(s):  
Phase Velocity ◽  
Electromagnetic Radiation ◽  
Particle Velocity ◽  
Electromagnetic Waves ◽  
Seismic Waves ◽  
Fundamental Difference ◽  
Radio Waves ◽  
Transverse Waves ◽  
The Difference ◽  
Wave Phenomena

Most waves can be defined by just a few parameters: period, frequency, wavelength, amplitude, particle velocity, phase velocity, and group velocity. ‘Waves in essence’ explains these parameters in turn and then goes on to discuss the spreading and fading of waves and the complexities of waves that arise through their interactions with objects and other waves resulting in diffraction and interference. It also describes the difference between longitudinal and transverse waves and the important wave phenomena of refraction and reflection. It then outlines the fundamental difference between pressure waves like sound, ocean, and seismic waves, and electromagnetic waves, which include light and radio waves. All electromagnetic radiation is made of particles called photons.

4. Windows in the sky

2016 ◽  
pp. 39-46
Author(s):  
Geoff Cottrell
Keyword(s):  
Solar Radiation ◽  
Electromagnetic Radiation ◽  
Electromagnetic Waves ◽  
Outer Space ◽  
Cosmic Ray ◽  
High Energy ◽  
Electromagnetic Spectrum ◽  
Radio Waves ◽  
Transverse Waves ◽  
The Universe

The atmosphere influences much of what can be seen through a telescope. Most of the atmosphere lies within 16 km from the Earth’s surface. Further out, the air becomes thinner until it merges with outer space. In the ionosphere—a layer 75–1000 km high—neutral atoms are ionized by solar radiation and high-energy cosmic ray particles arriving from distant parts of the Universe. ‘Windows in the sky’ explains electromagnetic radiation and the electromagnetic spectrum from gamma rays through to visible light and radio waves. Electromagnetic waves are transverse waves that can be polarized. The atmosphere acts as a filter and blocks cosmic electromagnetic radiation. Atmospheric turbulence distorts starlight resulting in ‘twinkling’ stars.

Determination of the velocity of short electromagnetic waves by interferometry

1952 ◽  
Vol 213 (1112) ◽  
pp. 123-141 ◽  
Keyword(s):  
Phase Velocity ◽  
Electromagnetic Radiation ◽  
Free Space ◽  
Electromagnetic Waves ◽  
Wave Beam ◽  
Wave Length ◽  
Wave Frequency ◽  
Space Wave

A new measurement of the velocity of electromagnetic radiation is described. The result has been obtained, using micro-waves at a frequency of 24005 Mc/s ( λ = 1∙25 cm), with a form of interferometer which enables the free-space wave-length to be evaluated. Since the micro-wave frequency can also be ascertained, phase velocity is calculated from the product of frequency and wave-length. The most important aspect of the experiment is the application to the measured wave-length of a correction which arises from diffraction of the micro-wave beam. This correction is new to interferometry and is discussed in detail. The result obtained for the velocity, reduced to vacuum conditions, is c 0 = 299792∙6 ± 0∙7 km/s.

6. Electromagnetic waves

2018 ◽  
pp. 70-99
Author(s):  
Mike Goldsmith
Keyword(s):  
Electromagnetic Radiation ◽  
Infrared Radiation ◽  
Electromagnetic Waves ◽  
Scientific Investigation ◽  
The Other ◽  
Electromagnetic Spectrum ◽  
X Rays ◽  
Radio Waves ◽  
History Of ◽  
Insight Into

‘Electromagnetic waves’ considers the history of the scientific investigation into the electromagnetic spectrum, including Einstein’s insight into the quantized nature of electromagnetic radiation. It explains that the only difference between light, radio waves, and all the other forms of electromagnetic radiation is the length of the fictitious-but-convenient waves or, equivalently, the energy of the photons involved. These different energies lead to different mechanisms for the formation and absorption of the different kinds of radiation, and it is this which gives rise to their different behaviours. Radio waves, microwaves, infrared radiation, light, ultraviolet light, X-rays, and gamma rays are all discussed.

Principles of Microwave Radiation

1980 ◽  
Vol 43 (8) ◽  
pp. 618-624 ◽  
Author(s):  
B. CURNUTTE
Keyword(s):  
Electromagnetic Radiation ◽  
Microwave Radiation ◽  
Food Processing ◽  
Electromagnetic Waves ◽  
Ultra Violet ◽  
X Rays ◽  
Radio Waves ◽  
Dual Nature ◽  
Ultra Violet Radiation ◽  
Transmission And Absorption

Microwaves, such as those used in cooking and processing food, are part of the broad spectrum of electromagnetic radiation which includes radio waves, microwaves, infrared radiation, visible light, ultra-violet radiation, x-rays and Gamma rays. Electromagnetic radiation has a dual nature, it is both wave-like and particle-like. An understanding of this dual nature of electromagnetic radiation is necessary for an understanding of the processes of emission, transmission and absorption of microwaves, which is in turn necessary for understanding the processes and phenomena which are important in the use of microwave radiation as a source of energy for heating and food processing. The properties of electromagnetic waves and the processes of emission. transmission and absorption are described and some effects in microwave-heating applications are discussed.

Phase memory and additional memory in W. K. B. solutions for wave propagation in stratified media

1976 ◽  
Vol 350 (1660) ◽  
pp. 27-46 ◽  
Keyword(s):  
Electromagnetic Waves ◽  
Seismic Waves ◽  
Memory Term ◽  
Radio Waves ◽  
Atmospheric Physics ◽  
Magnetohydrodynamic Waves ◽  
Acoustic Gravity Waves ◽  
Cumulative Change ◽  
Phase Memory ◽  
Additional Memory

For a wave travelling obliquely in a stratified inhomogeneous medium the W. K. B. solution contains a phase memory term that expresses the cumulative change of complex phase as the wave propagates. This memory may have two parts. One is the familiar phase memory displayed in all cases. The other is an additional memory that has recently been shown to be important for radio waves in an anisotropic ionosphere, but it is not present for an isotropic ionosphere. The subject is examined here for some other types of wave in geophysics and atmospheric physics. It is shown that there can be an important additional memory for atmospheric acoustic gravity waves, and a small additional memory in some other cases including seismic waves when Coriolis force is allowed for, and electromagnetic waves in a stratified optically active but isotropic medium. For magnetohydrodynamic waves there is additional memory if a gravitational field is present, but not otherwise.

scholarly journals Symmetry breaking of azimuthal thermo-acoustic modes in annular cavities: a theoretical study

2014 ◽  
Vol 760 ◽  
pp. 431-465 ◽  
Author(s):  
M. Bauerheim ◽  
P. Salas ◽  
F. Nicoud ◽  
T. Poinsot
Keyword(s):  
Symmetry Breaking ◽  
Electromagnetic Waves ◽  
Seismic Waves ◽  
Theoretical Study ◽  
Stable Configuration ◽  
Splitting Strength ◽  
The Difference ◽  
Acoustic Instabilities ◽  
The Stability ◽  
Two Parameters

AbstractMany physical problems containing rotating symmetry exhibit azimuthal waves, from electromagnetic waves in nanophotonic crystals to seismic waves in giant stars. When this symmetry is broken, clockwise (CW) and counter-clockwise (CCW) waves are split into two distinct modes which can become unstable. This paper focuses on a theoretical study of symmetry breaking in annular cavities containing a number $N$ of flames prone to azimuthal thermo-acoustic instabilities. A general dispersion relation for non-perfectly-axisymmetric cavities is obtained and analytically solved to provide an explicit expression for the frequencies and growth rates of all azimuthal modes of the configuration. This analytical study unveils two parameters affecting the stability of the mode: (i) a coupling strength corresponding to the cumulative effects of the $N$ flames and (ii) a splitting strength due to the symmetry breaking when the flames are different. This theory has been validated using a 3D Helmholtz solver and good agreement is found. When only two types of flames are introduced into the annular cavity, the splitting strength is found to depend on two parameters: the difference between the two burner types and the pattern used to distribute the flames along the azimuthal direction. To first order, this theory suggests that the most stable configuration is obtained for a perfectly axisymmetric configuration. Therefore, breaking the symmetry by mixing different flames cannot improve the stability of an annular combustor independently of the flame distribution pattern.

ENERGY OF ELECTRIC CHARGE RADIATION AND ITS EFFECTS

2021 ◽  
Vol 0 (4) ◽  
pp. 5-8
Author(s):  
V.D. PAVLOV ◽  
Keyword(s):  
Angular Momentum ◽  
Electromagnetic Radiation ◽  
Electric Charge ◽  
Electromagnetic Waves ◽  
Circular Path ◽  
Proved Theorem ◽  
Centripetal Acceleration ◽  
Starting Point ◽  
The Difference ◽  
Accelerated Charge

It is believed that an electric charge moving along a circular path, i.e. with centripetal acceleration, it is necessary to emit electromagnetic waves. This applies, inter alia, to cyclotron radiation. The purpose of the work is to establish the conditions for the radiation of an electric charge, based on the significant differences between its tangential and centripetal accelerations. The relevance of the work is determined by the widespread use of devices that generate electromagnetic radiation due to the acceleration of electric charges, including X-ray units and magnetrons. The starting point is a credible statement. A number of mathematically correct transformations are performed with it. Therefore, the result is necessarily reliable. Sad experience shows that this logic is not available for many specialists. In the event that such a necessary reliable result contradicts the existing paradigm, preference is almost always given to the paradigm, regardless of the persuasiveness of the evidence. This circumstance is an almost insurmountable obstacle to obtaining new knowledge. After all, if it does not contradict the paradigm, then it is not new and does not represent any value. Electromagnetic radiation carries away energy. It follows from this that the energy of the radiating system changes during radiation. Associated with this is the well-known rule: the change in energy is equal to the perfect work. Four theorems are proved. Theorem 1. A tangentially accelerated charge emits electromagnetic waves. Theorem 2. A normally accelerated charge does not emit electromagnetic waves. Theorem 2 formalizes a circumstance well-known in mechanics that the centripetal force does not perform work (since the scalar product of orthogonal vectors must be zero). Theorem 3. Electric charge satisfies Newton's second law. When a hydrogen-like atom passes from one stationary state to another, the orbital angular momentum changes. The difference is attributed to a photon and is called the photon's spin. Theorem 4. The spin of a photon is zero. The defect in the angular momentum of an atom during radiation can easily be attributed to the nucleus of an atom and even to an electron.

REFLECTION COEFFICIENT OF AN ELECTROMAGNETIC WAVE IN CONDUCTIVE MEDIA

2018 ◽  
pp. 100-106
Author(s):  
M. S. Sudakova ◽  
M. L. Vladov ◽  
M. R. Sadurtdinov
Keyword(s):  
Reflection Coefficient ◽  
Ground Penetrating Radar ◽  
Electromagnetic Waves ◽  
Water Contamination ◽  
Survey Design ◽  
Direct And Inverse Problems ◽  
The Difference ◽  
Ground Penetrating ◽  
Ideal Dielectric

Within the ground penetrating radar bandwidth the medium is considered to be an ideal dielectric, which is not always true. Electromagnetic waves reflection coefficient conductivity dependence showed a significant role of the difference in conductivity in reflection strength. It was confirmed by physical modeling. Conductivity of geological media should be taken into account when solving direct and inverse problems, survey design planning, etc. Ground penetrating radar can be used to solve the problem of mapping of halocline or determine water contamination.

Attenuation of dispersed wave trains

1962 ◽  
Vol 52 (1) ◽  
pp. 109-112
Author(s):  
James N. Brune
Keyword(s):  
Phase Velocity ◽  
Group Velocity ◽  
Seismic Waves ◽  
Free Oscillations ◽  
Wave Trains

Abstract It is shown that groups of seismic waves are attenuated by the factor exp −exp⁡−πXQUT where X is the distance, U the group velocity, T the period and Q−1 is a measure of the damping of free oscillations. Accordingly, observations of Q given by Ewing and Press (1954 a, b) and Sato (1958) are revised by the ratio of the phase velocity to the group velocity.

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