Question

(a) A person is suffering from both myopia and hypermetropia.
(i) What kind of lenses can correct this defect?
(ii) How are these lenses prepared ?
(b) A person needs a lens of power + 3D for correcting his near vision
and -3D for correcting his distant vision. Calculate the focal lengths
of the lenses required to correct these defects.​

Answer 1

Answer:

Myopia and hypermetropia are both easily corrected at Optical Masters using prescription glasses or contact lenses specifically designed to counteract the effect. For myopia, a concave lens (minus powered) is placed in front of a myopic eye, moving the image back to the retina and clarifying the image.

A person suffering from myopia as well as hypermetropia uses spectacles having bifocal lenses in which upper part consists of a concave lens (to correct myopia) used for distant vision and the lower part consists of a convex lens (to correct hypermetropia) used for reading purposes.

Explanation:

Answer 2

Answer:

(i)myopia can be corrected by concave lens whereas convex lens can be used to correct hypermetropia

b)power = 1/f

if power = +3D

than f= 0.33 m ( convex )

if power = -3D

f = -1/3 = - 0.33 m

-ve sign indicates concave lens