Elements of natural philosophy (Volume 2-3) . ill be reflect-ed, or not, from the analyzer, according as the plane ofreflexion there coincides with, or is perpendicular to, theplane of first reflexion. In the latter case, a hlacJc crosswhite or black will be displayed on the screen, and in the former a white that But the case is different with the vibrations whichwm be resolved; emerge at any 0ther point, such as L. The principal section of the crystal for these vibrations, neither coincideswith, nor is perpendicular to, the plane of primitive po-larization ; and consequent-ly t
Elements of natural philosophy (Volume 2-3) . ill be reflect-ed, or not, from the analyzer, according as the plane ofreflexion there coincides with, or is perpendicular to, theplane of first reflexion. In the latter case, a hlacJc crosswhite or black will be displayed on the screen, and in the former a white that But the case is different with the vibrations whichwm be resolved; emerge at any 0ther point, such as L. The principal section of the crystal for these vibrations, neither coincideswith, nor is perpendicular to, the plane of primitive po-larization ; and consequent-ly the incident polarizedwave will be resolved intotwo, within the crystal,whose planes of polariza-tion are respectively paral-lel and perpendicular tothe principal section 0 vibrations in these two waves are reduced to the same plane by means of theReduced to the analyzer; they will, therefore, interfere, and the extent same plane by . the analyzer, and oi that interference will depend upon their difference of interfere. phase. Fig. ELEMENTS OF OPTICS. 359 Now, the difference of phase of the two waves varies Extent ofwith the interval of retardation. When this interval isinterference dependent on an odd multiple of half a wave length, the two waves difference ofwill be in complete discordance; and, on the other hand, phase*they will be in complete accordance, and will unite theirstrength, when the retardation is an even multiple of thesame quantity. The successive dark and bright lineswill, therefore, be arranged in circles. § 168. We have been speaking here of homogeneous Phenomenali^ht. When white or compound light is used, the rings Prodllced witu & . white light; of different colors will be partially superposed, and theresult will be a series of iris-colored rings separated bydark intervals. All the phenomena, in fact, with the ex-ception of the cross, are similar to those of Newtonsrings; and we now see that they are both cases of thesame fertile principle,—th
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