Elementary treatise on physics, experimental and applied : for the use of colleges and schools (1906)
Ganot, A. (Adolphe), 1804-1887, Atkinson, Edmund, 1831-1901, Reinold, A. W. (Arnold William), 1843-1921 · New York : Wood · leaf 587
Fig. 540 away than Y ; L and / are called conjugate foci, for if either is a source oflight the other is its image. As the point of light comes nearer the lens, the convergenceof the emergent rays decreases, and the focus / becomes more distant ;when the point Lcoincides with theprincipal focus,… … 1 ig- 511 As the refracted rays are parallel in this case, the intensity of light onlydecreases slowly, and a simple lamp can illuminate great distances. Itis merely necessary to place it in the focus of a double convex lens, as shownin fig. 541. Virtual foci.—When a luminous point is placed…
Physics
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