Question

A student uses spectacles of focal length - 2-5 m.
(a) Name the defect of vision he is suffering from.
(b) Which lens is used for the correction of this defect?
(c) List two main causes of developing this defect.
(d) Compute the power of this lens.​

Answer 1

Answer:

f= - 2.5 m

a) Since, the focal length is negative, it is a concave lens and it is used in myopia

b) Concave

C) Elongated eyeballs or decreased focal length due to abnormal curvature

D) power= 1/f

=1/-2.5

= -10/25

= -0.4Dioptre

Answer 2

Answer:-a)if focal length is in negative,then it means that he is suffering from "MYOPIA"

B)concave lens can be used to correct this problem.

C)due to elongation in eyeball and focal length is decreased due to abnormal curvature