Elements of natural philosophy (Volume 2-3) (1850)
Bartlett, W. H. C. (William Holms Chambers), 1804-1893 · New York : Barnes · leaf 220
here by making spherical concave m = - 1, Which reduces it tO, reflector; 1_ f 2^r 1 7 (43) But two cases can arise, and these are distinguished bythe sign of the radius. The reflector may be concavetowards incident light, in which case r will be positive,or it may be convex towards the same… … Principal focaldistance; Hence the principal focal distance is equal to half radius,and Equation (43), reduces to 1_ / 1 F 1 f /A4\ Equation for^ / discussion; Now, this Equation is only concerned with the re-flected wave, and if this wave be concentrated at allafter deviation, it must be upon that…
Mechanics · Acoustics · Optics
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