Progressive lenses are an update on bifocal and trifocal lenses. Both of these more traditional types of glasses have telltale lines in the lenses. Progressives have a seamless look.

Trifocal glasses have three distinct prescriptions on the lens, indicated by lines, to correct faraway, intermediate, and near vision. Progressive lenses blend the prescriptions so that there are ...

To correct this defect, a person is prescribed bifocal lens that has both types of lenses convex and concave. Aditya, Jaunpur ...

The properties of concave and convex lenses were first described around the year 1000, although magnifiers in the form of lens-shaped crystals or glass may have been used much earlier.

We compare and contrast concave and convex lenses by drawing ray diagrams. In this Closer Look segment on Lenses, we compare and contrast concave and convex lenses by drawing ray diagrams and ...