ch, as regards power, all lenses may be referred. Thestandard or unit which has been almost universally adopted is, as is wellknown, a lens having a true focal length of one meter, its power being termedDiopter or Dioptric. The kind of lenses most generally used have spherical surfaces, and theycan… … /Negative\VMeniscus/Thinner in the middle than at the edge Fig. U the edge, have a convergent effect on the rays of light; the second group,thinner in the middle than at the edge, have a divergent effect. These differentforms are shown in Fig. 14. 21 B A U S C H L O M B
Lenses · Eyeglasses
Internet Archive · California Digital Library · Public Domain Mark 1.0. Free to use for anything.
