Millikan, Robert Andrews, Gale, Henry Gordon · Boston : Ginn and Co. · leaf 451
Fig. 428. The pupil dilates when the light is dim and contracts whenit is intense relaxed, the lens has just the proper curvature to focus planewaves upon the retina, that is, to make distant objects dis-tinctly visible. But by directing attention upon near objectswe cause the muscles which hold…
Physics
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