A Treatise on Geometrical Optics

aberration achromatic angle of divergence angle of incidence angular angular aperture aperture apparent distance axis caustic centre characteristic function colours convergent convex coordinates cos² cosec curvature cusp direction direction-cosines dispersion emergent ray equal equation eye-glass eye-piece eye-ring F₁ F₂ field of view focal length focal plane formula geometrical focus given Hence illumination image formed incident ray index of refraction lenses linear magnification magnifying power normal adjustment object-glass obtain optical order of approximation origin of light orthotomic curve orthotomic surface parallel rays pencil of rays perpendicular plane mirror point of incidence positive principal focus principal plane prism radii ratio ray passes reduced path reflected ray refracting surfaces refractive index retina Shew sin² small object small pencil sphere spherical surface telescope theorem thin lens unit plane unit points vertex x₁ y₁ µ² дк