. Polarisation of light . Fig. viiL] POLARISATION OF LIGHT. 103 are similar ellipses having the longer diameter of theone coincident with the shorter of the other, and themotion in the two oppositely directed. The longerdiameters of the ellipses coincide with the directionsof vibration of the ordinary and extraordinary raysin the case of an ordinary positive crystal ; and areconsequently directed the one toward the centre ofthe figure, the other in a direction at right angles tothe first. The exact or even approximate determination ofthe figures produced is a complicated question, andrequ
. Polarisation of light . Fig. viiL] POLARISATION OF LIGHT. 103 are similar ellipses having the longer diameter of theone coincident with the shorter of the other, and themotion in the two oppositely directed. The longerdiameters of the ellipses coincide with the directionsof vibration of the ordinary and extraordinary raysin the case of an ordinary positive crystal ; and areconsequently directed the one toward the centre ofthe figure, the other in a direction at right angles tothe first. The exact or even approximate determination ofthe figures produced is a complicated question, andrequires mathematical analysis for its solution, but ageneral idea of their nature may nevertheless be easilyformed. When the polariser and analyser are eitherparallel or crossed, circular rings are formed, andtowards the outer parts of the field traces of the blackcross are seen, which grow stronger as we proceedoutwards from the centre—that is, towards the partswhere the rays are more oblique, and where thepolarisation more nearly
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Keywords: ., bookcentury1800, bookdecade1870, bookpublisherlondo, bookyear1874
