Elementary optics and applications to fire control instruments (1922)
United States. Army. Ordnance Dept · Washington, Govt. Print. Off. · leaf 29
gure25 occurs at an an-gle of incidence lessthan the critical an-gle, and the surfaceat which this reflec-tion takes place istherefore silvered. The triple mirrorshown in figure 2Ghas three reflectingfacts which are mu-tually orthogonal.It has the peculiarproperty of deviat-ing any ray whichenters… … 26 If 11 angles are accurately made, this parallelism is true, no matterhow the prism is turned so long asit receives the incident light. Useis made of this prism in signallingdevices and in the internal adjust-ment device of small range finders.The penta prism illustrated in fig-ure 27 is used in…
Optics · Optical instruments · Fire control (Gunnery) -- Optical equipment
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