A Person With a Myopic Eye Cannot See Objects Beyond 1.2 M Distinctly. What Should Be the Type of Corrective Lens Used to Restore Proper Vision?

The type of corrective lens used to restore proper vision is concave or diverging lens.

Step 1. a formula for calculating lens power

The faraway point appears to be infinity to a normal eye. The lens should be set up so that a virtual image of an object at infinity appears at 1.2 metres.

Here is a formula to determine a lens’s power:

P = 1/f

In this case, the focal length is f and the lens’s power is P.

The relation is

1/f = 1/v – 1/u

Where v = image distance and

u = object distance.

Step 2. Determine the corrective lens’s power to get your eyesight back to normal.

Given that, a person cannot directly perceive objects farther than 1.2 metres.

Consequently, to see the distances beyond 1.2 metres from the indicated

v = -1.2 m

u = -∞

f = ?

Substituting the values in the relation, we get,

1/f = 1/-1.2 – 1/(-∞)

1/f = -1/1.2

On simplifying we get

f = -1.2 m

Substitute focal length in the power of lens formula, we get,

P = 1/-1.2

P = -⅚

P = -0.83 D

The corrective lens will be divergent or concave if the wearer has myopia.

Therefore, the power is -0.83 D has to be used to restore proper vision.