. Light, a textbook for students who have had one year of physics. RINGS AND BRUSHES 235 for this case. The phase-difference between ordinary and extra-ordinary will depend upon the inclination and length of thepath within the crystal, for instance it will evidently be greaterfor the ray FD than for ED, since FD is more inclined to theaxis and has also a longer path within the crystal. The square area in figure 122 represents the crystal slipas seen from above, the optic axis now being perpendicular tothe paper. Let 0 be the point of emergence of the axial rayCd of figure 121, and AB the plane
. Light, a textbook for students who have had one year of physics. RINGS AND BRUSHES 235 for this case. The phase-difference between ordinary and extra-ordinary will depend upon the inclination and length of thepath within the crystal, for instance it will evidently be greaterfor the ray FD than for ED, since FD is more inclined to theaxis and has also a longer path within the crystal. The square area in figure 122 represents the crystal slipas seen from above, the optic axis now being perpendicular tothe paper. Let 0 be the point of emergence of the axial rayCd of figure 121, and AB the plane of polarization of the inci-dent light. Referring back to figure 121, it is clear that thephase-difference that exists between the components of the ray. Figure 122 ED will be the same as for any other ray such as ED whichemerges from the crystal at the same distance from the point0 of figure 122. Therefore, if in the latter figure we drawcircles about 0, the phase-difference between the ordinary andthe extraordinary rays on emergence will be the same for allpoints on any one circle, but different for points on differentcircles. Circles are drawn for which this phase difference is ir,2tt, 3tt, 4ir, respectively. Consider first the light that comes through at points alongthe line AB. For these points the principal plane is the same -ii LIGHT as the plane of polarization, therefore there is no extraordinaryray and all the light passes through as ordinary light, Nexttake points along CD. For these the principal plane is per-pendicular to the plane of polarization of the incident light,and therefore there is no ordinary ray, and all the light comesthrough as extraordinary ray with its plane of polarization un-altered. Points along AB and C
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectlight, bookyear1921
