Waves, electric frequency

Traveling-wave tubes (frequency range 0.3 to 50 GHz, invented by Kompfner,47 usually part of a traveling-wave amplifier, Fig. 10.13) are low-Q amplifiers for microwaves, with typically a four-decade frequency range the tube is a long vacuum tube, in which the magnet focuses an axial electron beam, while the helix, fed externally by a small microwave beam, acts as a delay line whose electric field bunches the electrons this induces even more electrons to travel along the helix the amplification is as much as 70 dB. 

Capacitors are used to store electric energy, especially for shorter periods of time, and substitute -> batteries in some cases. They smooth the output of full or half-wave rectifiers in power supplies or are part of electric frequency - filters. 

According to classical electrodynamics, an accelerated particle with electrical charge emits an electromagnetic wave. In case of an particle oscillating with the frequency v a wave with frequency v is emitted. The intensity of the wave depends on the angle 0-between the direction of emission and the vector 3 which lies perpendicular to the direction of acceleration v (see Fig. 8 a) and is given by... 

The amplitudes of the electric and magnetic vectors in a plane electromagnetic wave, of frequency (t /2jr), travelling in a direction parallel to the propagation vector v, vary with time t and position r as does... 

The frequency effect of ultrasonic waves with frequencies around 1 MHz (0.76, 1.0, and 1.7 MHz) was studied using the electrical detection method described above [88], The experimental data and theoretical analysis of the results indicated that there was an optimum ultrasonic frequency corresponding to a maximum in sonochemical yield according to the bubble distribution in liquid. A Gaussian distribution of gas bubble radii was expected for a water sample exposed to a normal air atmosphere. In addition, experimental data also showed that any comparison of the frequency effect on the sonochemical efficiency should be under the conditions of not only the same sonic power but also the same sonic intensity. 

Of course, the frequencies and wave vectors fulfil the phase-matching conditions. The third-order susceptibility Xijw is a fourth-rank tensor having a priori 81 elements. In an isotropic material, there remain 21 non-vanishing elements, among which only three are independent [69]. The simplest case consists in a unique incident plane wave, linearly polarized. Indeed, the third-order polarization vector is then parallel to the electric field and reduces to the sum of two propagating terms, one oscillating at the wave circular frequency co, and another at the circular frequency 3(o. The amplitudes of these two contributions write, respectively. 

By assuming that an optical electron of momentum p natural frequency rw, and restoring force k = mm x is acted upon by a force due to the electric field of an electromagnetic wave of frequency oj. Van Vleck and Weisskopf ... 

The origin of Raman spectra can be explained by an elementary classical theory. Consider a light wave of frequency v with an electric field strength E. Since E fluctuates at frequency v, we can write... 

This solution for the electric field contains both traveling wave (imaginary part of the exponential function) and attenuated wave (real part of the exponential function) contributions. The traveling wave with frequency , travels at a reduced velocity in the medium compared to vacuum, ncolc). 

The second-order NLO properties are of interest for a variety of NLO processes [1-3]. One of the most relevant is the SHG, originated by the mixing of three waves two incident waves with frequency co interact with the molecule or the bulk material with NLO properties, defined by a given value of the quadratic hyperpolarizability, fi, or of the second-order electrical susceptibility, respectively, to produce a new electrical wave, named SH, of frequency 2co. Another important second-order NLO process is the electrooptic Pockels effect which requires the presence of an external d.c. electric field, E(0), in addition to the optical E co) electrical field. This effect produces a change in the refractive index of a material proportional to the applied electric field, and can be exploited in devices such as optical switches and modulators [1-3]. 

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