Elementary optics and applications to fire control instruments (1922)
United States. Army. Ordnance Dept · Washington, Govt. Print. Off. · leaf 33
oximation: sin / = —u h (17) sin?=-^p Equation 16 then becomes u — r ur-u~^u which may be written 1 1 _ u u 2r (18) The focal length, which will be denoted by/, is equal to the recip-rocal of the right hand member of equation 14. It should be noted that in the case here selected / is… … -Parallel rays projected bymirror. The approximations which were made in equation 17 have a simplephysical interpretation. A ray from O, incident upon the mirror atI, cuts the axis OV at a point nearO. If I is considered as a variablepoint approaching V as a limit, thenthis point is also variable…
Optics · Optical instruments · Fire control (Gunnery) -- Optical equipment
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