scholarly journals On the nature of wireless signal variations—I

1927 ◽  
Vol 115 (771) ◽  
pp. 291-305 ◽  
Keyword(s):  
Continuous Wave ◽  
Wave Length ◽  
Length Change ◽  
Path Difference ◽  
Angle Of Incidence ◽  
Continuous Change ◽  
Interference System ◽  
Variable Nature ◽  
Wireless Signal ◽  
Magnetic Vectors

In a recent communication two experimental methods of investigating the atmospheric deflection of electric waves have been described. In one of these methods interference phenomena, which take the form of a succession of signal maxima and minima at the receiving station, are artificially produced by a small continuous change of transmitter wave-length. From the study of these phenomena information relating to the path difference and relative intensities of the ground and atmospheric waves may be deduced. In the second type of experiment the angle of incidence of the down-coming waves is deduced from an examination of the electric and magnetic vectors in the stationary interference system produced at the ground by the waves incident from above and reflected at the earth’s surface. In a more recent communication some further results, obtained by means of the “wave-length change” method, have been described, which indicate that the variations of signal intensity produced at moderate distances from a continuous-wave transmitting station are due to the variable nature of the rays returned from the upper atmosphere, and not to slight variations of transmitter wave-length. In this second communication, however, certain points were left unelucidated. For example, it was pointed out that the wave-length change experiments gave us no information as to the relative importance of the parts played by changes in intensity, phase polarization, or angle of incidence of the downcoming waves in producing the ordinary nocturnal signal variations. The development of the second type of experiment mentioned above (in which the electric and magnetic vectors of the stationary interference system produced at the ground are examined) has yielded considerable information on these and allied points, and it is with these developments that the present communication deals. The refinements in the technique of the original experiments may be grouped under three heads. In the first place, we have employed automatic photographic registration for recording the galvanometer deflections corresponding to the magnitudes of various vectors. Such registration is specially useful when simultaneous records of the variations of any two vectors are required.

scholarly journals On some measurements of the equivalent height of the atmospheric ionised layer

1930 ◽  
Vol 126 (803) ◽  
pp. 542-569 ◽  
Keyword(s):  
Wave Length ◽  
Length Change ◽  
Early Morning ◽  
Path Difference ◽  
Research Station ◽  
Angle Of Incidence ◽  
Continuous Change ◽  
Primary Object ◽  
Atmospheric Disturbances ◽  
Aerial Systems

In previous communications various experimental methods of examining the characteristics of downcoming wireless waves have been described. Of these methods by far the most useful has proved to be that which involves a small continuous change of transmitter wave-length, by means of which there is produced at a receiving station a succession of interference maxima and minima between ground waves and waves deviated by the upper atmosphere. By using loop and antenna receiving systems in several different ways it has been possible to estimate, from a comparison of the interference “fringe” amplitudes, the relative intensities of the ground and atmospheric waves and also the angle of incidence of the latter at the ground; while a comparison of the phase differences between the two sets of waves, as deduced from the interference “fringes” recorded on different types of aerial systems, has yielded information relating to the polarisation of downcoming waves. In all such investigations, however, the number of “fringes” produced by a known wave-length change has been found, even when the determination of that number was not the primary object of the experiment. In this way the equivalent path difference for the ground and atmospheric wave tracks has been calculated as a routine measurement from which the equivalent height of the ionised layer could be deduced. In the course of such investigations carried out at the Peterborough Radio Research Station, much evidence has therefore accumulated relating to the diurnal variation of the equivalent height of those regions in the atmosphere which are responsible for the deviation of wireless waves. As was pointed out in the first communication dealing with the work of the station, considerable interest is, in the study of wireless wave propagation, attached to the transitional periods of sunrise and sunset. As the experiments under discussion were usually carried out on wave-lengths of from 300 to 600 metres ( i. e ., on frequencies of from 1000 to 500 kilocycles per second) the study of the sunset period was, except on rare occasions, impossible, because of interference from broadcasting transmitters. The majority of the tests therefore took place during the sunrise period when, in addition to the advantage of the low level of artificial interference, there was also that of the early morning minimum of natural atmospheric disturbances. In carrying out such early morning runs it was soon found that, in the few hours before sunrise, the signal records showed the presence of both primary and secondary interference maxima and minima, indicating the simultaneous reception of two or more downcoming rays. After sunrise the phenomena became simpler and smooth “fringes” were recorded. This latter particular period was therefore especially suitable for the determinations of the characteris­tics (intensity, angle of incidence, polarisation, etc.) of downcoming waves already described. The present communication, is in part an attempt to elucidate these pre-sunrise phenomena and in part an introduction to two papers which are to follow, since it was the study of the significance of multiple downcoming rays which led to the investigation of the subject with which these two papers respectively deal, namely, the simultaneous reception of downcoming waves at several receiving stations and the use of shorter wave-lengths.

scholarly journals On wireless interference phenomena between ground waves and waves deviated by the upper atmosphere

1926 ◽  
Vol 113 (764) ◽  
pp. 450-458 ◽  
Keyword(s):  
Short Distance ◽  
Wave Length ◽  
Path Difference ◽  
Upper Atmosphere ◽  
Wireless Transmission ◽  
Continuous Change ◽  
Carrier Wave ◽  
Night Time ◽  
Side Band ◽  
Atmospheric Waves

In previous communications we have outlined two experimental methods of examining the effects of the atmospheric ionized layer in short-distance wireless transmission. In the first type of experiment the existence of night-time interference phenomena between two sets of waves was demonstrated by changing the wave-length of the transmitter continuously through a small range and observing the resultant maxima and minima of signal intensity. It was suggested that such interference took place between ground waves and waves deviated through large angles by the upper atmosphere. In the second type of experiment the angle of incidence of such atmospheric waves at the earth’s surface was measured by comparing the magnitude of the electric and magnetic forces in the stationary wave system produced at the ground. The results of these experiments were interpreted as yielding a direct experimental proof of the existence of the Kennelly-Heaviside layer, and also as demonstrating that the “fading” of broadcasting signals at moderate distances from the transmitter was due mainly to interference phenomena between two sets of waves arriving at a receiver with an appreciable path difference. But there still remained the problem of the cause of the natural succession of interference effects which constitutes fading at moderate distances, and which takes place continuously throughout the night-time. These variations indicate either that the phase relation between the ground and atmospheric waves is continually changing at night, or that intensity or polarization changes of the atmospheric waves are taking place. In considering possible causes of phase variations, let us examine the relation between the path difference and the wave-length for a typical case of short-distance transmission. Let D represent the path-difference between the ground and atmospheric rays. Then the atmospheric ray arrives n wavelengths behind the ground ray at the receiver, where n = D/ λ , and λ is the wave-length. It has been mentioned above that a possible cause of the natural signal variations which occur at night is a continuous change of phase which would be produced by a change in n . Such a change might be brought about by changes in D, or in λ , or in both simultaneously, and it is necessary to decide between these possibilities. Changes in D might be brought about by a variation in the height of the layer, so that a Döppler effect at "reflection” is produced. In such a case the signal variation might be regarded as the beating between the ground-ray frequency and the reflected-ray frequency. On the other hand, if there is a slow variation of transmitter frequency, the frequency of the atmospheric ray would be different from that of the ground ray, because of the difference in times of emission from the transmitter, and, again, the natural changes might be regarded as beats. The suggestion has already been made by Breit that fading is due to the modulation of the carrier wave, and thus to change of wave-length. In the latter connection we have to consider the variation of both carrier wave and side-band frequencies. The results of our earlier experiments suggested that the change of side-band frequency necessary for the wireless transmission of music is sufficient to produce selective frequency fading, and thus a certain amount of distortion. But with the normal type of modulation the signal intensity is chiefly dependent on the intensity of the carrier wave, and the question whether a slow “swing” of the carrier wave is responsible for such fading (which is observed whether the carrier wave is modulated or unmodulated) seems still unanswered. The question, of course, is equally of interest in both continuous wave telegraphy and wireless telephony.

The effect of temperature on the reflexion of X-rays

1937 ◽  
Vol 33 (3) ◽  
pp. 380-384 ◽  
Author(s):  
M. Blackman ◽  
R. H. Fowler
Keyword(s):  
Wave Length ◽  
Path Difference ◽  
Effect Of Temperature ◽  
Angle Of Incidence ◽  
X Rays ◽  
Ideal Crystal ◽  
Mean Square ◽  
Glancing Angle ◽  
The Mean ◽  
Image Position

1. The reflexion of X-rays from an ideal crystal would be independent of temperature if the particles forming the crystal were at rest. Because of the motion of the particles a temperature effect does exist. It can easily be seen that only the component of the displacement at right angles to the reflecting plane is of importance, since it is the path difference between such planes which matters. The complete theory has been worked out by Debye and by Waller. The result is that, owing to the influence of the temperature, the intensity is multiplied by a factor e−2m, whereHere and μs is the mean square of the component of the displacement (in a direction at right angles to the reflecting planes) due to a normal mode π is the glancing angle of incidence of the X-rays on the reflecting planes, and λ is the wave-length.

scholarly journals Solar Tracker

2020 ◽  
Vol 2 (1) ◽  
pp. 59-65
Author(s):  
Irfan Danial Hashim ◽  
Ammar Asyraf Ismail ◽  
Muhammad Arief Azizi
Keyword(s):  
Fossil Fuels ◽  
Electrical Energy ◽  
Maximum Amount ◽  
Solar Panel ◽  
Angle Of Incidence ◽  
The Sun ◽  
Continuous Change ◽  
The Earth ◽  
Solar Tracker ◽  
Rotation Of The Earth

Solar Tracker The generation of power from the reduction of fossil fuels is the biggest challenge for the next half century. The idea of converting solar energy into electrical energy using photovoltaic panels holds its place in the front row compared to other renewable sources. But the continuous change in the relative angle of the sun with reference to the earth reduces the watts delivered by solar panel. Conventional solar panel, fixed with a certain angle, limits their area of exposure from the sun due to rotation of the earth. Output of the solar cells depends on the intensity of the sun and the angle of incidence. To solve this problem, an automatic solar cell is needed, where the Solar Tracker will track the motion of the sun across the sky to ensure that the maximum amount of sunlight strikes the panels throughout the day. By using Light Dependent Resistors, it will navigate the solar panel to get the best angle of exposure of light from the sun.

scholarly journals On the total photo-electric emission of electrons from metals as a function of temperature of the exciting radiation

1926 ◽  
Vol 112 (762) ◽  
pp. 599-630 ◽  
Keyword(s):  
Wave Length ◽  
Ultra Violet ◽  
Electric Activity ◽  
Simple Relation ◽  
Exciting Radiation ◽  
Angle Of Incidence ◽  
Positive Elements ◽  
Activity Frequency ◽  
Exciting Frequency ◽  
Electric Effect

In the year 1913 K. T. Compton and O. W. Richardson ('Phil. Mag.,' vol. 26, p. 549 (1913)) published a paper containing an important investigation on the action of homogeneous mono-chromatic radiation on a number of metals. The essential characteristics of the photo-electric activity of various metals are set out in their experimental curves obtained by plotting photo-electric yield of electrons against exciting frequency. These curves contain double maxima in the case of extremely electro-positive elements like Na, and one maxium for a less electro-positive metal Al, while the curves for Pt exhibit no maximum in the range of frequencies covered by their experiments. Later investigations by Souder ('Phys. Rev.,' vol. 8, p. 327 (1916) and O. W. Richardson and A. F. A. Young ('Roy. Soc. Proc.,' A, vol. 107, p. 377 (1925)) have confirmed these general characteristics of photo-electric activity-frequency curves. A photo-electric maximum for the "selective" effect was observed by Pohl and Pringsheim ('Verh. d. Deutsch. Physik. Ges,' vol. 11. p. 1039 (1910)) as early as 1910 in the case of some electro-positive elements. The general shape of the humps in their curves appears to be a function of the angle of incidence of the exciting radiation; nevertheless, the position of the maximum is quite independent and definite. Lately, R. Döpel ('Zeits. für Phys.,' Vol. 33, p. 237 (1925)) has shown that a less electo-positive metal like Sr also shows the photo-electric maximum. It is therefore probable that all metals would exhibit such maximum. It is therefore probable that all metals would exhibit such maximum photo-electric effect if it were possible to extend the range of exciting frequencies far into the ultra-violet. The presence of double maxima in the curves for Na and K probably points to the existence of two photo-electric thresholds in these elements, as suggested by O. W. Richardson ('Proc. Phys. Soc. London,' vol. 36, p. 388 (1924)), and may lead to interesting developments in future. In the following Table I are collected the observed values of the long wavelength limit λ 0 and the wave-length λ m of the maximum photo-electric effect. A comparison of the figures in columns 1 and 3 shows that the frequencies v 0 and v m can be correlated within the range of accuracy and consistency attainable in photo-electric measurements by a simple relation, v m = 3/2 v 0 .

ELECTROMAGNETIC LATERAL WAVES OBSERVED BY EARTH‐SOUNDING RADARS

Geophysics ◽  
1976 ◽  
Vol 41 (6) ◽  
pp. 1126-1132 ◽  
Author(s):  
John W. Clough
Keyword(s):  
Electromagnetic Waves ◽  
Critical Angle ◽  
Continuous Wave ◽  
Angle Of Incidence ◽  
Lateral Wave ◽  
Snell’S Law ◽  
Snell's Law ◽  
Low Amplitude

Electromagnetic waves refracted at the critical angle according to Snell's law give rise to the lateral wave. The low amplitude lateral wave is usually obscured by other waves when continuous wave sources are used. Using a pulsed source (radar) and continuously recording echoes reflected from within dielectric earth materials as a function of angle of incidence, records are produced which clearly show the lateral wave. In some earth‐probing applications, the lateral wave may predominate and proper identification of its characteristics is important.

scholarly journals The reflection and diffraction of X-rays

1931 ◽  
Vol 133 (821) ◽  
pp. 274-291 ◽  
Keyword(s):  
Critical Angle ◽  
Close Agreement ◽  
Wave Length ◽  
Length Distribution ◽  
Incident Beam ◽  
Electromagnetic Theory ◽  
Spherical Mirror ◽  
Angle Of Incidence ◽  
X Rays ◽  
Carbon Target

The agreement between the theories of the reflection of X-rays by solids and observations is discussed. Generally the observations so far obtained are not in close agreement with each other or with theory. The writers find that X-rays of wave-lengths 13·3 Å. (Cu Lα) and 44·7 Å. (C Kα) are reflected by glass, quartz and stainless steel at angles considerably greater than the calculated critical angles. The radiation from carbon has been focussed by a spherical mirror for an angle of incidence of 45°. The ratio of the intensity of the reflected to the incident beam, when X-rays from a carbon target are incident on a glass mirror, has been determined approximately by a photographic method and is found to agree with the Fresnel electromagnetic theory provided a higher absorption of the X-rays occurs than has been previously supposed. This evidence of reflection for angles of incidence greater than the critical angle, which is 6° for glass at a wave-length of λ = 44·7 Å., is confirmed by observations with a glass diffraction grating with which the λ = 44·7 Å. line has been observed for angles of incidence on a plane grating up to 19°. A new plane ruled grating spectrometer is described by means of which the C Kα line has been obtained with short exposures in all orders from the 18th negative to the 13th positive. Microphotometer curves of the wave-length distribution of the energy in the grating spectrum of carbon radiation are given, and these indicate that it consists almost entirely of the Kα line, λ = 44·7 Å. Using Rowland’s method of coincidences the wave-length λ C kα is found to be 44·7 5 Å. relative to λ Cu Lα = 13·32 Å.

scholarly journals EFFECT OF WAVE-CURRENT INTERACTION ON THE WAVE PARAMETER

1982 ◽  
Vol 1 (18) ◽  
pp. 28
Author(s):  
Yu-Cheng Li ◽  
John B. Herbich
Keyword(s):  
Wave Height ◽  
Wave Length ◽  
Wave Theory ◽  
Length Change ◽  
Numerical Calculations ◽  
Wave Parameter ◽  
Linear Wave ◽  
Linear Wave Theory ◽  
Wide Range ◽  
Non Linear

The interaction of a gravity wave with a steady uniform current is described in this paper. Numerical calculations of the wave length change by different non-linear wave theories show that errors in the results computed by the linear wave theory are less than 10 percent within the range of 0.15 < d/Ls s 0.40, 0.01 < Hs/Ls < 0.07 and -0.15 < U/Cs i 0.30. Numerical calculations of wave height change employing different wave theories show that errors in the results obtained by the linear wave theory in comparison with the non-linear theories are greater when the opposing relative current and wave steepness become larger. However, within range of the following currents such errors will not be significant. These results were verified by model tests. Nomograms for the modification of wave length and wave height by the linear wave theory and Stokes1 third order theory are presented for a wide range of d/Ls, Hs/Ls and U/C. These nomograms provide the design engineer with a practical guide for estimating wave lengths and heights affected by currents.

THE REFLECTION OF ELASTIC WAVES FROM TRANSITION LAYERS OF VARIABLE VELOCITY

Geophysics ◽  
1937 ◽  
Vol 2 (4) ◽  
pp. 357-363 ◽  
Author(s):  
Alfred Wolf
Keyword(s):  
Elastic Constants ◽  
Elastic Waves ◽  
Wave Length ◽  
Continuous Functions ◽  
Angle Of Incidence ◽  
Variable Velocity ◽  
Transition Layers ◽  
Coefficient Of Reflection ◽  
Continuous Waves ◽  
Explicit Formulae

Elastic waves are reflected not only from discontinuities in the medium in which they are propagated, but also from transition layers in which the elastic constants are continuous functions of position; the coefficient of reflection is then a function of wave length. Section 1 of this paper gives explicit formulae for the coefficient of reflection of continuous waves from such a layer, at vertical incidence. In Section 2 the manner of variation of the coefficient of reflection with the angle of incidence is discussed qualitatively. Finally, in Section 3, the shape of a pulse reflected from a transition layer is determined.

scholarly journals The luminous efficiency of monochromatic rays entering the eye pupil at different points and a new colour effect

1937 ◽  
Vol 123 (830) ◽  
pp. 90-118 ◽  
Keyword(s):  
White Light ◽  
Wave Length ◽  
Monochromatic Light ◽  
Luminous Efficiency ◽  
Visual Sensitivity ◽  
Angle Of Incidence ◽  
Apparent Brightness ◽  
Point Of Entry ◽  
In Transit ◽  
Considerable Range

It has been found by the writer, in collaboration with B. H. Crawford (1933), that light rays entering the eye pupil near its periphery are less efficient in producing the impression of brightness than rays entering centrally, the patch of retina stimulated (the fovea) being the same in both cases. Reasons were put forward in the paper cited for thinking the effect to be retinal in origin, i. e. due to a variation of visual sensitivity with angle of incidence of the light on the retina, rather than the result of a greater absorption of the peripheral rays in transit through the optic media of the eye. Most of the observations were made with white light and, although the absence of any pronounced coloration of the field illuminated by the peripheral ray indicated that the reduction of apparent brightness could not be very different for different colours, it was considered desirable to test this point directly by observations with monochromatic light throughout the spectrum. In Part I of this paper an investigation on these lines is described from which it appears that for the writer’s eye the ratio of the luminous efficiencies of rays entering centrally and peripherally varies systematically to a limited extent in passing through the spectrum. It was also found that within a considerable range of intensity the value of the ratio for a given wave-length is independent of intensity. Since the publication of the original paper, Dziobek (1934) and Wright and Nelson (1936) have both made measurements confirming the existence of a marked variation of luminous efficiency with point of entry. The latter workers employed white light and coloured lights obtained with the aid of filters. Goodeve (1936) has also measured the effect, in the extreme red.

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