What is the power of the lens, if the far point of a short-
sighted eye is 200 cm?

The far point of a myopic (short-sighted ) person is 80 cm in front of the eye. What is the power of the lens required to enable him to see very distant objects clearly.

The near point of a hypermetropic (long -sighted ) person is 75 cm from the eye . What is the power of the lens required to enable the person to read clearly a book held at 25 cm from the eye ?

(a) What is long-sightedness ? State the two causes of long-sightedness (or hypermetropia). With the help of ray diagrams, show : (i) the ray-defect long-sightedness. (ii) correction of long-sightedness by using a lens. (b) What eye has a near point distance of 0.75 m. What sort 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 ? 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 ?

The ability of the lens in human eye to change the power of the lens to be able to see the near and far off distances is called the power of __________,

The near point of a hypermetropic eye is 1 m. What is the nature and power of the lens required to correct this defect ? (Assume that the near point of the normal eye is 25 cm).