Johnson's natural philosophy and key to philosophical charts : illustrated with 500 cuts; being reduced photographic copies of all the diagrams contained in the author's philosophical series of indestructible school charts ; for the use of schools and families (1878)
of light, that fornithe image, are brought to a focus before they reach the retina, as shownby the image T, of the object A, which falls short of the retina. Theobject will be seen, but not distinctly. To obtain distinct vision, there-fore, the object must be brought nearer to the eye, or concave… … Long-sightedness, on the contrary, is caused by too little curvature ofthe cornea and crystalline lens, which throws the image S, of the objectA, beyond the retina. This defect, therefore, is corrected by holdingthe object at a greater distance from the eye, or by employing convexspectacles, either…
Physics · Astronomy
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