polarize

t. [Eng. polar; -ize.] To affect with polarity. pō-lar-ized, pa. par. or a. [POLARIZE.] Having polarity; affected or acted upon by polarization. polarized-rings, s. pl. Optics: Imagine a crystal symmetrical around a single axis, like a section of the trunk of a tree, with the elasticity greatest or least in the direction of the axis, and symmetrically alike all round the circumference. If we cut a plate in the way of a plank, it will behave like the films already spoken of. But if a slice be cut acro the trunk at right angles it must be different, when a ray of light pa es through in the direction of the axis. The ether vibrations are at right angles to the path of the ray (now the same as the axis), but in all these directions the elasticity is equal, consequently a beam of common light will not be doubly refracted, nor a beam of plane-polarized light further resolved, in pa ing along the axis. This is borne out by cutting a plate of calcite at right angles to its axis. But if the ray pa es through such a plate obliquely, double refractions and interference will come into action, and we shall perceive color. Imagine now a conical, or strongly convergent pencil of plane-polarized light trayersing the plate, and the analyzer turned so as to extinguish the light pa ing the polarizing Nicol. The center of the plate, where the beam is truly polarizer axial, will still appear dark. But, as the light becomes more and more oblique, the vibrations will be resolved into some plane pa ing through the axis, and planes at right angles to these, or tangential planes. In perpendicular and horizontal planes, these will cause no further resolution of the vibrations, and there will therefore be a black cro when the analyzer is cro ed; but in all other planes, the more and more oblique light must cause succe ive rings of light and darkne , or, when white light is employed, of color. In crystals which are not perfectly symmetrical about one axis, the ideal structure may be compared to that of a tree trunk of an oval section. Here, a plank would still give two polarizing planes, as in a film of selenite; but a transverse section would also show two rectangular elasticities. In such a case, analysis proves that there must be two lines or axes inclined to each other, in which there can be no double refraction, and that the fringes of color must take the general shape of lemniscates. In many crystals the properties are quite different for light of different wave-lengths, and in some the plane of the axes is at right angles for one end of the spectrum to what it is for the other. The relation of the elasticities may also be profoundly changed by heating the crystal, so that the intermediate one becomes greatest or least; in such cases, as in heating selenite, the double rings gradually merge into one, and then the two rings spread out again in a direction at right angles to the former. Generally, it may be said that cubic crystals po e no double refraction; that crystals symmetrical round one axis are uniaxial, doubly-refracting, and exhibit circular rings; and that other crystals are bi-axial, and exhibit double rings. All these phe nomena are of the greatest importance in the study of rocks, and the fragments of crystals imbedded in them.