Carpenter, William Benjamin, 1813-1885, Dallinger, W. H. (William Henry), 1842-1909 · Philadelphia, Blakiston · leaf 39
and a screen to receive the imageof the object are so adjusted that the image of the object becomes equalin size to the object itself. The distance of the object from the screendivided by 4 gives the focal length of the lens. If a radiant be placed between a lens and its principal focus, therays on… … Fig. 15.—Rays diverge when a radiant is placed between a lens and itsprincipal focus. Focus of divergent rays is virtual. meet in a point. This is called the virtual conjugate focus of theradiant. The principal focus of a concave (or diverging) lens isshown in fig. 16. It will be seen that the…
Microscopy
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