(a) Myopia is the scientific name of short-sightedness.
(b) Hypermetropia is the scientific name of long-sightedness.
(a) What is long-sightedness ? State the two causes of long-sightedness (or hypermetropia). With the help of ray diagrams, show : (i) the eye-defect long-sightedness. (ii) correction of long-sightedness by using a lens. (b) An eye has a near point distance of 0.75 m. What short of lens in spectacles would be needed to reduce the near point distance to 0.25 m ? Also calculate the power of lens required. Is this eye long-sighted or short-sighted ? (c) An eye has a far point of 2 m. What type of lens in spectacles would be needed to increase the far point to infinity ? Also calculate the power of lens required. Is this eye long-sighted or short-sighted ?