Magnetic waves

FIGURE 1.1 Electromagnetic wave. At any time the elongations of the electric wave E(x) and of the magnetic wave H(x) into space appear perpendicnlar to each other. The fignre shows two full periods of the electromagnetic wave. 

When materials are irradiated by X-rays, several effects occur, e.g. absorption, scattering, and X-ray fluorescence. The heat should be generated by the absorption of electro-magnetic wave even by X-ray as shown in Fig. 1. The heat generation was actually observed in, for example, the deterioration of a silicon single crystal by strong X-ray. However, so much attention has not been paid in scientific sense to this phenomena. 

E0exp( — k" x) and H0exp( —k" x) are the amplitudes of the electric and magnetic waves, and = k x — ut is the phase of the waves. An equation of the form K x = constant, where K is any real vector, defines a plane surface the normal to which is K. Therefore, k is perpendicular to the surfaces of constant phase, and k" is perpendicular to the surfaces of constant amplitude. If k and k" are parallel, which includes the case k" = 0, these surfaces coincide and the waves are said to be homogeneous if k and k" are not parallel, the waves are said to be inhomogeneous. For example, waves propagating in a vacuum are homogeneous. 

In order to describe an electro-magnetic wave (light), we need to know the following characteristics ... 

Figure 9.6—Representation of an electromagnetic i rave. Atany point on the xOy plane, the component of the magnetic wave can be dissociated into two half vectors bt and b2 rotating with opposite velocities. Only b2 can interact with the nuclei of population E2-...

From Fig. 11.6 it can be seen that the polarisation (and so the refractive index) increases as it approaches a resonance frequency and temporarily falls to a "too" low value just beyond it. This remarkable and sudden change in behaviour was once considered anomalous and was called anomalous dispersion. The electro-magnetic wave theory showed that the "anomalous" dispersion is just as "normal" dispersion and can be explained as a direct consequence of the equation of motion of nuclei and electrons. 

Magnetic properties are important in the function of electronic devices. An example is the use of yttrium iron garnet (YIG) in microwave devices. On applying an external magnetic field to a YIG disk, the input, say energy of one particular frequency selectively passes to the output. Thin films based of YIG within which magnetic waves can pass have proven to be useful. The use of lanthanides in magnetic devices as transducers is listed in Table 12.18. 

Microwave propagation in carbon black/epoxy resin composites shows that for small particle size inclusions, magnetic wave propagation increases with filler concentration but for large particles the propagation of magnetic waves does not depend on the concentration of the inclusions. ... 

Hartree, D.R., The propagation of electro-magnetic waves in a refracting medium in a magnetic field, in Proc Cambridge Phil Soc 27, 143, 1931. 

The diffraction of electrons can also be regarded as a special case of the electro magnetic wave equation, where the electrostatic potential of the atom replaces electron density ep (X-ray diffraction). This potential is composed of the effect of the atomic nucleus and that of the electron cloud. The spatial distribution of the potential corresponds approximately to that of the electron density, but falls off less rapidly. The maxima of the Fourier series, however, correspond in both cases to the position of the atomic nucleus. 

Plasmon surface polaritons (PSPs) or surface plasmons are transverse magnetic waves that propagate along a metal-dielectric interface, their field amplitudes decaying exponentially perpendicular to the interface [29,30]. Their dispersion relation is given by... 

---