Laurence, Lionel · London, School of Optics · leaf 254
xis cuts the latter, is in terms of i— M/=r=r/2 cos ?=2F ~F/cos i. From the above a/r=sin i=\ 1 - cos2 i; . < /^& A /4F2-o2. whence cos i= V 5- = v —,^Q rl 4F2 Substituting these values in the previous formula we get M/in terms ofa, the semi-aperture M/W - ,-2/2Vr2-a2=2F - 2F2/a/4F2 - a2.… … Caustic Curve.—Those rays diverging from a point which are within afew degrees of the principal axis, unite in a point, which is taken as the focus.Those rays having larger and larger angles of incidence (Fig. 261), are re-flected to cut the principal axis nearer and nearer to the vertex of the…
Optics
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