Elementary optics and applications to fire control instruments (1922)
United States. Army. Ordnance Dept · Washington, Govt. Print. Off. · leaf 40
ding from the point O which are re-fracted by the lens pass through the line 1, h. This line is there-fore a real image of the point O. If the refracted rays are produced backward through the lens,they are seen to pass through the line I3 I^. This line is thereforea virtual image of the point O.… … Fig. 40.—Action of eylindrical lens. 01 at right angles. In general, a cylindrical lens forms two suchimages of a point and as the position of the object or type of lens ischanged, they may be both real, both virtual, or one real and onevirtual, as in the illustrated case. In the last two drawings…
Optics · Optical instruments · Fire control (Gunnery) -- Optical equipment
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