Question

A myopic person can see up to 2m calculate the power of the lens used to coreect it

Answer 1

This defect is myopia.

It can be defined is as follows.

The eye defect in which a person cannot see objects beyond near point or far objects but can see the near objects clearly is called Myopia.

The point of maximum distance at which the eye lens can form an image on the retina is called ' far point '

This defect can be corrected by using biconvex lens.

Given distance of far point (D) = 2m

Let f be the focal length of eye lens.

Image distance ( distance between eye lens and retina ) for our human eye is always constant and is about 2.5 cm.

This is due to the action of ciliary muscles.

applying lens formula, we get

f = -D

= -2 cm.

but , the power of a lens is reciprocal of focal length.

hence. Power = 1/f. ( f in meters )

= 1/-2

= - 0.5 dioptre

Answer 2

$u \: = - \infty \\ v = - 2m$

Using lens form formula

$\frac{1}{v} - \frac{1}{u} = \frac{1}{f}$

so f= -2m

p=1/F

p=1/-2

p = -0.5D

so. the person should use concave lens of P = -0.5 D