Polarization

“ Not only is the oblique direction of maximum polarization more definite and the polarization itself more complete, but the observation is easier than with white light in consequence of the uniformity in the colour of the light scattered in various directions. If we begin with a blue glass, we may observe the gradually increasing obliquity of the direction of maximum polarization; and then by exchanging the blue glass for a red one, we may revert to the original condition of things, and observe the transition from perpendicularity to obliquity over again. ”

“ Not even yet have we terminated the enumeration of the co-existent polarities which in this province of nature have been brought into view. Light has polar properties; the very term polarization is the record of the discovery of these. The forces which determine the crystalline forms of bodies are of a polar nature: crystalline forms, when complete, may be defined as those forms which have a certain degree of symmetry in reference to opposite poles. ”

“ The light, however, which has thus been polarized, may be wholly, or in part, depolarized by the interposition of many crystallized bodies, the degree of depolarization being dependent on the more or less exact position of a certain neutral axis or plane of their crystalline texture with the plane of primitive polarization. When these planes are perfectly coincident, the light remains polarized in that plane, and a black line appears in that direction ”

“ Whenever the precipitated particles are sufficiently fine, no matter what the substance forming the particles may be, the direction of maximum polarization is at right angles to the illuminating beam, the polarizing angle for matter in this condition being invariably 45°. ”

“ Sect. 4.—Explanation of Polarization by the Undulatory Theory. Even while the only phenomena of polarization which were known were those which affect the two images in Iceland spar, the difficulty which these facts seemed at first to throw in the way of the undulatory theory was felt and acknowledged by Young. Malus’s discovery of polarization by reflection increased the difficulty, and this Young did not attempt to conceal. ”

“ Since reflexion and refraction, even of the ordinary kind, modify the polarization of light, we may expect to find this effect produced when rays of light are made to pass through media of regularly varying density. It is accordingly found that all transparent bodies which are sufficiently elastic to admit of different positions of their particles round a given state of equilibrium, as glass, crystals, animal jellies, horn, &c. produce phænomena of polarization when they are compressed or expanded, or made unequally dense by being considerably heated and then cooled suddenly and unequally. ”

“ In each of these cases the alternations of light and darkness are most strongly marked, and the colors (if a quartz plate be used) are most vivid, or, in technical language, the polarization is most complete, when the light is reflected from each substance at a particular angle. In proportion as the inclination of the light deviates from this angle the colors become fainter, until, when it deviates very greatly, all trace of polarization at last disappears. ”

“ When a ray of light has undergone polarization in a certain direction, by the process above described, it carries that property with it, and preserves it without sensible alteration, when made to pass perpendicularly through even considerable thicknesses of air, water, and, in general, any substance that exerts only single refraction, but double refracting media alter, in general, the polarization of a ray, and in a manner, to all appearance, sudden, communicating to it a new polarization of the same nature in a different direction. ”

“ Let the coloring-matter represent the magnetism in the body charged, and we have the magnet illustrated in its polarization: the deep-red end is the positive pole, and the white or faintly-colored end is the negative pole.
It is a law of polarization that the positive poles of different magnets repel each other, and the negative poles repel each other; while positive and negative poles attract each other. The same law of polarization rules in electric or magnetic currents as in magnets at rest. ”

“ The phenomena of polarization are seen to accommodate themselves so thoroughly to this theory, that a simple approximation of the two is sufficient to prove that the one is the law of the other. Having thus coördinated the phenomena, the author considers in separate chapters "Circular Polarization," "Phenomena produced by Mechanical Means," "Atmospheric and other Polarization," "Figures produced by Crystal Plates," and "Composition of Colors by Polarized Light." The subject last named is illustrated by means of two very beautiful chromo-lithograph plates.
What is Music? ”

“ Having done this for the sake of Polarization, we turn to the phenomena of Double Refraction, and inquire what new hypothesis they require. But the answer is, that they require none: the supposition of transverse vibrations, which we have made in order to explain Polarization, gives us also the law of Double Refraction. Truth may give rise to such a coincidence; falsehood cannot. Again, the facts of Dipolarization come into view. But they hardly require any new assumption ”

“ Light is also polarized by reflection from the surface of a transparent medium. When a ray of ordinary light falls on a plate of glass at an angle of 54° 55 ́ with the normal, the reflected ray is perfectly polarized, and at other inclinations the polarization is incomplete. Here then is polarization by reflection. Fig. 207 shows an apparatus for producing this phenomenon. The light foiling on the first mirror from E is reflected through the tube as a polarized beam, and this is analyzed by the other mirror (I) , whose plane can be rotated round the axis of the tube. ”

“ Similarly any other ray scattered horizontally is perfectly polarized, and the vibration is performed in the hori- zontal plane. In other directions the polarization becomes less and less complete as we approach the vertical.
The observed facts as to polarization are thus readily explained,
and the general law connecting the intensity of the scattered light with the wave-length follows almost as easily from con- siderations of dimensions. ”

“ 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. ”

“ 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. ”

“ If this explanation is correct, precisely the same phænomena would be obtained by gradual heating as by successive reflexions in the interior of the Fresnel's rhomboid, but with this difference, that instead of the direction of the polarization varying by successive steps we should expect a continual transition through all degrees of elliptic polarization. The experiments confirm this perfectly. ”

“ The angle of polarization differs with different substances according to their refractive power, for polarization of the reflected ray is perfect only when the angle of incidence is such that the reflected ray is at right angles to the refracted one. ”

“ From each of the mutually seceding poles lines of polarization issue at definite angles, which (like elliptical radii on the periphery) meet at the sides of the newly produced crystal. Then again between these radii tension arises, so that the fibres become lamellæ. The main line between the two mutually seceding poles is the central line or polar axis of the crystal; the angular lines which determine the position of the lamellæ, are the polar radii. The polar radii determine the nucleus of the crystal and are therefore nuclear lines ”

“ The word polarization, borrowed from optics, where it has an unequivocal sense, serves likewise to designate the development of the counter electro-motive force of galvanic elements, and also that essentially different condition of badly conducting substances that is brought about by the simultaneous influence of quantities of opposite electricity. ”

“ The polarization of light, as it has been unfortunately called—unfortunately, as conveying an idea of determinate and different points or poles, which only exists in hypothetical analogy—presents to us a class of phenomena which promise to unclose the mysterious doors of the molecular constitution of bodies. ”

“ A more pronounced case of elliptic polarization by reflection is afforded by metals Formulae for metallic reflection may be obtained from Fresnel’s expressions by writing the ratio sin i/ sin r equal to a complex quantity, and interpret in the imaginary coefficients in the manner explained above. The optical constants (refractive index and co-efficient of extinction) of the metal may then be obtained from observations of the principal incidence and the elliptic polarization then produced. ”

“ In short, if any mathematical or physical quantity is of the nature of a vector, as defined in Art. 11, then any body or particle to which this directed quantity or vector belongs may be said to be Polarized [2] , because it has opposite properties in the two opposite directions or poles of the directed quantity.
The poles of the earth, for example, have reference to its rotation, and have accordingly different names.
Meaning of the term 'Magnetic Polarization.' 382.] ”

“ Since the rotation of the polarization plane is connected with the fact, that the medium is not in accordance in all its properties with its mirror image, then the things said in § 51 are not applicable anymore. Nevertheless, everything becomes quite easy when we restrict ourselves to isotropic media. ”

“ 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. ”