. Physiological optics : being an essay contributed to the American encyclopedia of ophthalmology . in variousrefractive conditions (simple ametropias) of the eye. Figs. 103, 104and 105 attempt to show:—(a) the plane mirror in two positions, Mx 202 PHYSIOLOGICAL OPTICS and M2, (b) the cone of light, AKN, emerging from the retinal pointA (drawn as heavy lines), (c) the cone of light, KBN, emergent fromthe luminous point B after rotation of the mirror from position M1 toM2 (indicated by dotted lines), (d) the nature of the emergent rays,whether parallel, convergent or divergent and (e) the porti
. Physiological optics : being an essay contributed to the American encyclopedia of ophthalmology . in variousrefractive conditions (simple ametropias) of the eye. Figs. 103, 104and 105 attempt to show:—(a) the plane mirror in two positions, Mx 202 PHYSIOLOGICAL OPTICS and M2, (b) the cone of light, AKN, emerging from the retinal pointA (drawn as heavy lines), (c) the cone of light, KBN, emergent fromthe luminous point B after rotation of the mirror from position M1 toM2 (indicated by dotted lines), (d) the nature of the emergent rays,whether parallel, convergent or divergent and (e) the portion of thepupil which appears luminous. The diagrams are of necessity exag-gerated and the mirror in its second position not only rotated butslightly displaced in order to emphasize certain points. In Figs. 103and 104, representing emmetropia and hyperopia respectively, a por-tion of the emergent cone of light, AKN, is intercepted by the ob-servers eye situated back of the aperture in the mirror in positionMx; this being the primary position the pupil of the eye under observa- M, a, -Tl&K. Fig. 104.—Detailed Diagram of Mirror, Retinal Image and Reflex (Shadow) Movements in Hyperopia. tion is seen filled with a reddish glow: upon rotation of the mirrorinto a secondary position, as M2, a portion of the emergent cone BKN,passing into space between the limits of KG and NI as diagrammed,is intercepted and received by the observer. The eye sees as luminousthat portion of the pupil which sends rays to it, i. e., the portion KDin Figs. 103 and 104, while DN is dark because the rays which comefrom this point are not received by the observer or are, as anothermode of expression, intercepted by the iris of the observer. We see,therefore, that in emmetropia and hyperopia, using a plane mirror,the reflex will travel in the same direction as that in which the mirroris moved and will be followed by a shadow due to the fact that thelight from a portion of the pupil does not reach the observ
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