A FAR-SIGHTED LENS, A CONVEX LENS, A MAGNIFYING LENS, A POSITIVE LENS AND A PLUS LENS ARE DIFFERENT NAMES FOR THE SAME LENS.
It is called a far-sighted lens, because it is fitted to far-sighted eyes; a convex lens because it has an elevated surface, and is thicker in the center and thinner at the edges; a magnifying lens because it magnifies things and makes them look larger; a positive lens because it bends rays of light inwards and brings them to focus; a plus lens because it adds curvature to your eyes.
A NEAR-SIGHTED LENS, A CONCAVE LENS, A REDUCING LENS, A NEGATIVE LENS AND A MINUS LENS ARE DIFFERENT NAMES FOR THE SAME LENS.
It is called a near-sighted lens because it is fitted to near-sighted eyes; a concave lens because it has a depressed surface and is thinner at the center and thicker at the edges; a reducing lens because it reduces and makes things look smaller; a negative lens because it bends rays of light outwards and spreads them away from the focus; and a minus lens because it subtracts and lessens the curvatures of your eyes.
Plus and minus lenses are each subdivided into spherical lenses and cylinder lenses. They are designated as plus spherical and minus spherical lenses. They are designated as plus spherical and minus spherical lenses. They are also designated as plus cylinder and minus cylinder lenses. The spherical and cylinder curvatures are often ground on one lens. Formerly they used to grind the sphere on one side and the cylinder on the other side. Now, both are ground on one surface of the lens. It is a compound (toric) curvature. It is similar to an egg-shaped curvature.
The eyes, being spherical in shape, mostly, need and require spherical lenses.
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