Elements of natural philosophy (Volume 2-3) . ubstances into two classes Doubly refracting distinguished by their axes, which are said to be posi-tive when the extraordinary ray is between the ordina-ry ray and the axis, as in the case of rock crystal; andnegative, wThen the positions of these rays are reversedwith respect to the axis, as in Iceland spar. substancesclassified. To find anyvalue of theextraordinaryindex betweenthe maximumand minimum. § 146. Having ascertained by experiment the value ofthe ordinary index, which will be represented by m0,and the maximum or minimum value of the ext
Elements of natural philosophy (Volume 2-3) . ubstances into two classes Doubly refracting distinguished by their axes, which are said to be posi-tive when the extraordinary ray is between the ordina-ry ray and the axis, as in the case of rock crystal; andnegative, wThen the positions of these rays are reversedwith respect to the axis, as in Iceland spar. substancesclassified. To find anyvalue of theextraordinaryindex betweenthe maximumand minimum. § 146. Having ascertained by experiment the value ofthe ordinary index, which will be represented by m0,and the maximum or minimum value of the extraor-dinary index, according as the crystal has a positive ornegative axis, which will be represented by me; then, de-noting the space described by the wave before incidence,in the same time that the radius vector of the extraor-dinary wave is described, by unity, will the extraordi-nary index between m0, and me, be found by the fol-lowing law. Let an ellipsoid of revolution, Fig. (102), be conceived, ELEMENTS OF OPTICS, 341 Fig. 102. Bale;. having its centre (7, at the point,of incidence, its axis of revolutioncoincident with the optical axis(7X, of the crystal, and its polarto its equatorial radius in the in-verse ratio of the ordinary, to theminimum or maximum value of the extraordinary index of refraction, according as thcrystal belongs to the negative or positive class. Then,in all positions of the extraordinary ray, its index iseaual to the reciprocal of its length contained between Valuc °f ^- x ° extraordinary the centre and surface of the ellipsoid. index. The equation of a section of this surface through theaxis, referred to the centre, is A2y2 + B2 x2 = A2 jB3, and calling r, the length of the extraordinary ray be-tween the centre and the surface, and d, its angle ofinclination with the optical axis, it reduces to Equation of asection of thesurface ; AB AB r — ^ A2 sin2 d + B2 cos2 & ^B2 + {A2-B2)sm2t ; Value of radiusvector; denoting by me, the value of the ext
Size: 1746px × 1431px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, booksubjectmechanics, booksubjectopticsandphoto
