What is the optical power of glasses with a convex lens if the focal length is 20 cm? What are these glasses for?

f = 20 cm = 0.2 m.D -? The optical power of the lens D is determined by the formula: D = 1 / f, where f is the focal length of the lens. For a convex lens, the optical power is D> 0, for a concave lens, D <0. D = 1 / 0.2 m = 5 diopters. Such lenses are used for people who suffer from hyperopia and cannot see nearby objects.
Answer: the optical power of the glasses is D = 5 diopters.