. The principles of physics. s properties with respect to a fixeddirection, and that these fixed directions for the two rays areat right angles to each other. In short, a beam of light thustreated is not alike upon all sides, but has certain relations tosurrounding space other than direction. This property canbe given to light in various ways. To this phenomenon, how-ever produced, has been given the name ?polariaation? Slices of crystal of the mineral tourmaline, cut in planesparallel with their axes, are prepared and sold for opticalexperiments. If two of these slices similarly situated, as
. The principles of physics. s properties with respect to a fixeddirection, and that these fixed directions for the two rays areat right angles to each other. In short, a beam of light thustreated is not alike upon all sides, but has certain relations tosurrounding space other than direction. This property canbe given to light in various ways. To this phenomenon, how-ever produced, has been given the name ?polariaation? Slices of crystal of the mineral tourmaline, cut in planesparallel with their axes, are prepared and sold for opticalexperiments. If two of these slices similarly situated, as inFig. 307, be placed between the eye and a card pierced by ahole, the hole will be plainly visible. But if one of the slices be 1 The refractive index of Canada balsam is intermediate between tlie indices of thecrystal. 2 Newton came to the conclusion that each of the two rays had two sides ; andfrom the analogy of this two-sidedness with the two-endedness of a magnet the termpolarization arose. POLARIZATION OF LIGHT. 405. Fig. 307. Fig. 308. slowly rotated in a plane at right angles with the beam oflight, the hole will grow dimmer until the slice has passedthrough a quarter of a revolution (as represented in Fig. 308),when it the rotation becontinued, the holereappears, faint atfirst, but reaching itsmaximum brightnessat the end of another quarter-revolution. Thus, at suc-cessive quarter-revolutions it is alternately extinguished andrestored. It appears, then, that light which has passed through onetransparent slice of tourmaline differs so much from commonlight, that a second similar slice may act like an opaque body, and stop it action of the tour-maline may be com-pared to that of a grating(A, Fig. 309) formed ofparallel vertical rods,which will allow all vertical planes (as a a) to pass, but stopsthe planes (as c c) that are at right angles to these plane that has succeeded in passing one grating willreadily pass a second similarly pl
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectphysics, bookyear1895
