Question

Concave lens is used to correct
A. Myopia
B. Presbyopia
C. Hypermetropia
D. Cataract

Answer 1

Hint: A concave lens is made of two spherical mirrors attached to each other in a way that the curve of both mirrors faces each other inwardly. Concave and convex lenses are used to correct sight disorders.

Complete answer: Nearsightedness or Myopia is an eye disorder characterized by the focus of light in front of the retina instead of directly on the retina. This leads to blurriness in distant image formation. The person suffering from myopia is able to see his/her nearby objects. Headache and eye strain are the other symptoms of myopia. Retinal detachment, cataracts, and glaucoma can lead to severe near-sightedness. The cause of myopia is considered a combination of environmental and genetic factors. It is a refractive error. Myopia is attributed to the increased axial length of the eye. The lens of the eyes is attached to the ciliary body by a ligament tissue. It serves to refract and focus light on the retina. The elongation of the eyeball results in the focusing of the image in front of the retina. Wearing a concave lens can cure myopia. The concave lens diverges the light rays and helps in focusing the image on the retina.
a) Loss in the flexibility of the lens causes presbyopia. It is characterized by the image being focused behind the retina. Using a convex lens can cure it.
b) Hyperopia is characterized by too short an eyeball. The distant images appear clear and near-by objects seem blurry. It can be corrected by a convex lens.
c) The cataract is due to the opaqueness of the lens. Transmitting of light rays is blocked. This can be corrected by surgical replacement with an artificial lens.
Hence, the right answer is option A.

Note: The various causes of myopia are extending periods of focusing over near placed objects, more time spent indoors, or family history of myopia. Myopia is also associated with high socioeconomic class. It has experimented that allowing children to spend more time outside reduces the risk of myopia.