A Treatise on Geometrical Optics

aberration adjustment angle aperture apparent approximation axes axis bright caustic centre circle colours constant convergent coordinates cos² curvature curve denote determine deviation direction directly dispersion distance diverging emergent rays equal equation expression eye-glass eye-piece face field final focal length focal plane foci focus follows formula front function geometrical give given Hence illumination incident increases least lens lenses less light linear lines magnification measured medium meet mirror normal object object-glass obtain optical origin origin of light orthotomic surface parallel pass pencil perpendicular placed position primary principal focus principal plane prism produced Prove quantities radius ratio reduced path reflected refracted respectively seen Shew sin² small pencil sphere spherical substitute taken telescope thickness thin unit zero