Ocular refraction and the shadow test . spherical lens; also comparison f degree This phenomena will be explained by reference to figure 49, Irepresents the first position o: the lens, the visual line from the eye at E to the object A corresponding to the principal axis; II representsthe second position of the lens, the visual line now passed through aprism and the object while actually occupying the same position asbefore at A appears displaced to A toward the apex of the prism, (fig-ure 35) this gives foundation for the following law. IV/u-ii ail object is :wi-:^,-(/ tliroiii:;li a convex sp
Ocular refraction and the shadow test . spherical lens; also comparison f degree This phenomena will be explained by reference to figure 49, Irepresents the first position o: the lens, the visual line from the eye at E to the object A corresponding to the principal axis; II representsthe second position of the lens, the visual line now passed through aprism and the object while actually occupying the same position asbefore at A appears displaced to A toward the apex of the prism, (fig-ure 35) this gives foundation for the following law. IV/u-ii ail object is :wi-:^,-(/ tliroiii:;li a convex spherical /ens and thelens is nioicd laterally, the object appears to move in the opposite direc-tion. The amount of displacement that the object appears to undergo,depends upon the power of the prism (strength of the lens) and thedistance from the lens ot the object viewed. If the object were situ-ated at A, shown by II, figure 49, it would appear as displaced to Awhile if at B, a position nearer the lens, it would seem to be located at. Appearance of \ ;ure 50. al line seen tlirovigh convex spherical lens rotatlot displaced, no displacement of the line S L. :d about its centre but B; the distance from A to A is greater than that from B to B, thougheach is created by the same movement of the lens L. The stronger the lens and the greater the distance of the object fromit, the more rapid zvill be the movement of the object. If an object be viewed through a spherical lens, the lens may berotated upon its principal axis and the object will not be distorted bythe act of rotation. Figure 50 will illustrate the straight line S L seen through thelens in various positions rotated about its centre, so long as the lens isnot displaced but merely rotated, no change in the appearance of the L E N 49 object is created, for the spherical lens possesses like power in everymeridian. A spltcrical lens zlUI />,? rcci\i;i!i.::cd; first, br the fact thatupon rotating it no distortion occ
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