. The book of photography; practical, theoretical and applied. Fig. 715.— Principle of the Polariscope. The polariscope used with the micro-scope is in two parts; the polarisermounted in a sleeve to slide into the tubebeloAV the stage or into the substage (), and the analyser mounted in a tubeto fit over the objective or eyepiece (). Both the polariser and analyser con-sist of what is known as a Nicols prism,that is, a natural crystal of Iceland sparwhich has been cut in a plane lying be-tween its obtuse angles, m, n, o, p (), and the faces polished and cemented
. The book of photography; practical, theoretical and applied. Fig. 715.— Principle of the Polariscope. The polariscope used with the micro-scope is in two parts; the polarisermounted in a sleeve to slide into the tubebeloAV the stage or into the substage (), and the analyser mounted in a tubeto fit over the objective or eyepiece (). Both the polariser and analyser con-sist of what is known as a Nicols prism,that is, a natural crystal of Iceland sparwhich has been cut in a plane lying be-tween its obtuse angles, m, n, o, p (), and the faces polished and cementedtogether in their original position with Canada balsam. It is well known thatwhen a beam of light is passed through anordinary crystal of Iceland spar it isseparated or refracted into two distinctbeams of equal brilliancy, the crystal. Fig. 716.—Nicgls Pkism. having the property of double refraction(Fig. 717). One of these beams obeys theordinary laws of refraction, and is there-fore called the ordinary refracted ray ;it has a refractive index of 1-658. Theother beam does not obev these laws, and Fig. 717.—Double Eefraotion with Iceland is therefore known as the extraordinaryrefracted ray ; it has a refractive indexof 1486. When the Nicols prism is usedthe extraordinary ray, having a lower re-fractive index than the Canada balsam,(r53), passes through the prism a ray of
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectphotography, bookyear
