Oppius, GAIUS

1st cent. B.C. Biographer of Cæsar and Scipio. Fragments survive. O Optical Center. a converging meniscus, the optical center is entirely without it on the convex side; if a diverging meniscus, the point is on the concave side. In general this point is determined by drawing two parallel radii, one to each curved surface, and joining the points where these lines cut the surfaces: the intersection of this last line with the principal axis is the optical center.