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)
s foci are at double the distance; the principalfocus being at a distance equal to twice the radius of the curved sur-face (408). Formation of Images by Convex Lenses. ^18. Figure 40.—Formation of images by convex lens-es, ■when the object is twice the focal distance.—If an object^as AE, be placed… … radiant points. Draw the secondary axes AB and EF, and let the twOdots on the principal axis be the principal foci of the lens. The pointA being beyond the principal focus, its rays will meet on its secondaryaxis, at B, beyond the principal focus on the right; and, in the sameway, the rays from E…
Physics · Astronomy
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