. On the anomalies of accommodation and refraction of the eye, witha preliminary essay on physiological dioptrics. Fig. 30 immediately shows, of equal size. nNow, in proportion as —- becomes smaller, the second focal distance h> &.,n of the surface h2 becomes longer, and s approaches more and more to h, whose focal distance 7iL 0^ has remained unaltered. Lastly, if n -jjr =1, A, 0/ is infinitely large, and s therefore lies in hx. Then two images of s are no longer formed, but s coincides with its image in the point h{: the lens is changed into a single refracting surface, of which I have in
. On the anomalies of accommodation and refraction of the eye, witha preliminary essay on physiological dioptrics. Fig. 30 immediately shows, of equal size. nNow, in proportion as —- becomes smaller, the second focal distance h> &.,n of the surface h2 becomes longer, and s approaches more and more to h, whose focal distance 7iL 0^ has remained unaltered. Lastly, if n -jjr =1, A, 0/ is infinitely large, and s therefore lies in hx. Then two images of s are no longer formed, but s coincides with its image in the point h{: the lens is changed into a single refracting surface, of which I have in IV. shown how to recognise the cardinal points. While in the case that n becomes greater than n, the point & is removed forward, the point o deviates in the opposite direction, backwards. This nappears already from the fact, that, when —^ has become -A- 54 DIOPTRICS OF THE EYE. sequently only one refracting surface has remained, s comes to lie on thesurface of curvature hiy and o, on the contrary, in the centre of curvatureki (Fig. 33) (compare Fig. 17). It must, however, be more accurately <?. « proved, and at the same time shown, how the position of o may in thiscase also be found. n n In Fig. 34 -g is much smaller than — as it thence appears, that the focal distance of rays, parallel in the lens and refracted on the posteriorsurface, as h-> $.! = F.,, is three times greater than that of the same raysrefracted on the anterior surface, as hi while the radius of cur-vature h2 k2 is only \\ times greater than hi kv. If we draw from the point a, situated in the focal surface of hlt a ray ab c,directed to ku this passes through at b unrefracted to c. If, moreover,we draw in the lens a second ray c b, parallel to ab c and directed to k2,and prolong tMs to a in the focal surface of h>, we have in the lens twoparallel rays b c and V c. All the rays parallel in the lens now unite ineach of the focal surfaces into one point, whence it follows that a b c isrefr
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