Polarization (wave)

“ Since vorticity in a perfect fluid cannot be created or destroyed, the modification of the system which is to be analogous to an electric field must be a polarized state of the vortex motion, and light must be represented by a communication of this polarized motion from one part of the medium to another. Many distinct types of polarization may readily be imagined: for instance, if the turbulent motion were constituted of vortex-rings, these might be in motion parallel to definite lines or planes ”

“ The energy of any polarized state of vortex-motion would be greater than that of the unpolarized state; so that if the motion of matter had the effect of reducing the polarization, there would be forces tending to produce that motion. ”

“ On comparing the percentage of light polarized and the angles of incidence it is seen that they decrease together. No definite maximum was made out, but the existence of one near or beyond 60° is perhaps indicated by the fact that polarization was less easily observed on the evenings previous to June 29, and by the more rapid variation in the percentages on this and the two succeeding evenings. ”

“ To produce the polar and equatorial movements of the air, there must be an agent both at the equator and the poles to prevent such stability by constantly disturbing equilibrium there, and that agent is heat; therefore, whatever be the degree of depression due the polar barometer in consequence of axial rotation, such depression could, of itself, produce neither trade nor counter-trade wind; it could no more produce currents in the air than in the sea, nor could axial rotation produce a high barometer at one pole, a low barometer at the other ”

“ As a matter of fact, rapid changes in sky polarization indicate about the only thing that can be authoritatively asserted—namely, that the invisible particles behave much like the molecular constituents of the air. ”

“ When the wave brought by the polar currents arrives—coming as it does from regions where it naturally has less velocity—it does not at once acquire the velocity of the earth’s motion at the equator; and since the rotation of the earth is from west to east, this portion of the water lagging behind forms a stream or current which has an apparent motion from east to west, that is to say, apparent as regards the earth, but real in relation to the adjacent land and water. The trade winds, which in this zone blow constantly in the same direction, lend their aid in maintaining the equatorial current. ”

“ The second and third of the observations of July 1, in the list below, were made upon regions removed several degrees from the nucleus, but though the amount of polarization is somewhat less, and tends to confirm the above conclusion, the difference is hardly greater than would be accounted for by the errors of observation. Determinations of polarization at great distances from the nucleus were not possible, the light being too feeble. ”

“ If the primary ray is unpolarized, the light scattered north and south is entirely due to that component which vibrates east and west, and is therefore perfectly polarized, the direction of its vibration being also east and west. ”

“ On this basis we should expect that in the driest air at great heights, where the temperature is low and condensation has but just begun, and the dust particles are rare, there would occur the smallest aqueous particles reflecting light of the feeblest intensity but the largest percentage of polarization. Rayleigh has shown that it is quite possible that the molecules of oxygen and nitrogen constituting the atmosphere may also exercise a diffuse selective reflection, and contribute to the brightness and polarization that are mainly due to aqueous vapours. ”

“ Thus, without wind, we should have a perpetual and uniform system of tropical and polar currents; though without wind, Sir John Herschel maintains, [9] we should have no "considerable currents" whatever in the sea. In consequence of the diurnal rotation of the planet on its axis, each particle of oil, were resistance small, would approach the poles on a spiral turning to the east with a relative velocity greater and greater, until, finally, it would reach the pole, and whirl about it at the rate of nearly a thousand miles the hour. ”

“ A rotation of the plane of polarization is not, however, measured by an adjustment of the analyser, but by annulling the rotation with a compensator. This is made of two plates of quartz, cut normally to the optic axis and of opposite rotations, placed the one in front of the other: the thickness of the one plate is fixed, while that of the other can be varied, as it is formed of two equal prisms that can be moved over one another along their common face. ”

“ As soon as one wave passes, another, of the reverse polarity, always succeeds. I have never known this to fail, and it may be set down as an invariable rule. When the poles of the aurora are in unison with the poles of the current upon the line, its effect is to increase the current; but when they are opposed, the current from the battery is neutralized,—null. These effects were observed at times during Saturday, Saturday evening, and Sunday, but were very marked during Sunday evening. ”

“ Of polarimeters for the studiy of rotary polarization there are three principal forms. In Wild's polaristrobometer, light from a soda flame, rendered parallel by a lens, is polarized by a Nicol's prism, and after traversing the space into which the active substance is to be inserted, falls on a Savart's plate placed in front of an astronomical telescope of low power, that contains in its eyepiece a Nicol's prism, which with the plate forms a Savart's analyser. A web in the focal plane of telescope marks the point in the field at which the bands are to be made to disappear ”

“ Hence it would require only one sixth as long to raise the temperature of 1 gram of water 1° C. In other words, assuming that, in the meantime, all the incoming radiations are absorbed and that no heat is lost by conduction, convection or radiation, then it will require the radiations from Polaris to fall upon 1 square centimeter continuously for one million years in order to raise the temperature of 1 gram of water 1° C. In marked contrast with this value, the radiation from the sun which is transmitted by our atmosphere and falls upon an area of 1 sq. ”

“ The rotation of the plane of polarization by quartz was discovered in 1811 by Arago; if white light be used the colours change as the Nicol rotates—a phenomenon termed by Biot “rotatory dispersion.” Fresnel regarded rotatory polarization as compounded from right- and left-handed (dextro- and laevo-) circular polarizations; and Fresnel, Cornu, Dove and Cotton effected their experimental separation. Legrand des Cloizeaux discovered the enormously enhanced rotatory polarization of cinnabar, a property also possessed—but in a lesser degree—by the sulphates of strychnine and ethylene diamine. ”

“ Therefore it is manifest, say the cataclysmatists, that though the two hemispheres do receive annually the same amount of solar heat, yet the amount dispensed by radiation is very much greater on one side of the equator than the other. The total effect of the alternate cooling down on each side of the equator causes an accumulation of ice at the pole—when the nights are longest—sufficient, say they, to disturb the centre of gravity of the earth, causing it to take up its position on the icy side of the equator. As the ice accumulates, so is the water drawn over from the opposite hemisphere. ”

“ It's fine now. (except maybe for Faraday) ☺Coppertwig (talk) 01:37, 23 May 2009 (UTC) Please explain why scattering in the atmosphere would cause polarization. What's asymmetric? Oh, wait, I get it: it's the scattered light that's polarized. I changed the wording so it sounds more as if it's talking about the scattered light, rather than the light that is continuing to pass through the atmosphere in its original direction. You got it. The first paragraph of Modern Optics almost makes me feel like starting a new career in one of those fields! ”

“ Assuredly we cannot have a current from the poles without a contrary current to the poles. If we go into the arctic circle, we again find the westerly and northerly winds predominating. If the current from the equator follows the surface, the westerly winds ought to be south-west. If it be above the surface wind, then the surface wind is the polar current, and ought to be north-east. ”

“ That solar heat is in some way or other the primary cause of this great displacement, through the change in specific gravity from the cooling of water toward the polar zones, counterbalanced by a return, however slowly, of water from the equator to the Poles, may well take the place of more recondite theories, such as that exploded by Herschel, that the expansion of water by heat in the equatorial zone raises the level of the sea, and causes a flow down a gently-inclined plane toward the Poles. ”

“ Solar energy may seem to be propelled in waves, but that is due to the action of coexistent and diverse influences. A given form of organized energy does not proceed in waves but in direct lines. The presence of a second or a third form of force-energy may cause the stream under observation to appear to travel in wavy formation, just as, in a blinding rainstorm accompanied by a heavy wind, the water sometimes appears to fall in sheets or to descend in waves. ”

“ The polar calms and the return current.—Entering the polar regions obliquely, it is pressed upon by similar particles flowing in oblique currents across every meridian; and here again is a calm place or node; for, as our imaginary particle approaches the parallels near the polar calms more and more obliquely, it, with all the rest, is whirled about the pole in a continued circular gale; finally, reaching the vortex of the calm place, it is carried upward to the regions above, whence it commences again its flow to the north as an upper current, as far as the calm belt of Capricorn ”

“ The inequality of the solar action on the land and water, together with the tendency of the atmosphere to preserve an uniform density, is the cause of these periodically shifting currents. During the day the land acquires a temperature higher than that of the ocean, and the air over it is therefore rarefied and ascends, and the cooler air from the sea glides in to fill the partial vacuum produced. ”

“ When these moisture globules condense into drops of water the potential energy is set free and becomes active either as heat or electricity. The cloud gathers up the energy into a condensed form, and when the tension gets too great a discharge takes place between the cloud and the earth or from one cloud to another, which to an extent equalizes the energy.
In most cases of thunder and lightning it is only a discharge from cloud to cloud unequally charged. This does not relieve the tension between the earth and the cloud, but distributes it over a larger area. ”

“ To compensate this flow, air rushes on the earth's surface toward the equator, and as it also is deflected from its course by the same inertia of rotation, it appears in the tropics as a trade wind blowing from the northeast. However, the upper warm current does not flow all the way to the pole in the upper regions; it is gradually cooled down, and in about the thirtieth degree of latitude it begins to descend to the earth's surface, where it meets with the cold polar current. ”

“ Supposing a primary wave to be formed in the ocean by any such causes, then the falling of this will cause a second wave to be formed, existing as a ring round the first one. The combined action of the first and second wave will form a third one, and so the disturbance, starting from a point, will radiate in broadening circles. During the up and down motion of these waves, the energy which is imparted to any particle of water will, on account of the work which it has to do in displacing its neighbours, by frictional resistance, gradually grow less and less, until it finally dies away. ”

“ Those of greater bulk, taking the ground, offer a resistance against which the lesser masses can only strain and grind; but away out in the unfathomable depths of the Polar Sea there is no chance of the [Pg 192] ice ever grounding. It is always floating, and so always susceptible to the force of wind, tide, and current. Consequently it is always moving and feeling the pressure of the water below, of the grinding strain of the drift, and of the surface disturbances brought about by the constant displacement. ”

“ If we regard, for instance, the polar current—that broad current which flows down from the unknown polar regions between Spitzbergen and Greenland—and consider what an enormous mass of water it carries along, it must seem self-evident that this cannot come from a circumscribed and small basin, but must needs be gathered from distant sources, the more so as the Polar Sea (so far as we know it) is remarkably shallow everywhere to the north of the European, Asiatic, and American coasts. ”

“ There is, therefore, a constant tendency with the air that these upper currents carry polarward to be crowded out, so to speak—to slough off and turn back. Thus the upper current is ever ready to supply the trade-winds, as they approach the equator, with air exactly at the right place, and in quantities just sufficient to satisfy the demand.
224. How is it drawn down from above?—This upper air, having supplied the equatorial cloud-ring (§ 514) with vapour for its clouds, and with moisture for its rains, flows off polarward as comparatively dry air. The dryest air is the heaviest. ”