Question

(a) A student suffering from myopia is not able to see distinctly the objects placed beyond 5 m. list two possible reasons due to which this defect of vision may have arisen. With the help of ray diagrams, explain
(i) why the student is unable to see distinctly the objects placed 5 m from his eyes.
(ii) the type of the corrective lens used to restore proper vision and how this is correct by the use of this lens.

Answer 1

There are some possible reason due to this defect of vision may have arisen :

(a) elongation of eyeball

(b) excessive curvature of the lens.

(i) student unable to see distinctly the objects placed beyond 5m from his eyes because student suffering with myopia . A myopic eye can't see distinct object clearly but able to see nearby object clearly.

(ii) convex lens of suitable focal length is used to restore proper vision. After using convex , image formed at retina. While before it , image was formed near the retina .

b. Focal length of convex lens is positive

So, f = +5m

Now, Power = 1/f = +1/5 = +0.2D

Hence, power is +0.2 diopter