The far point of a myopic person is 80 cm in front of the eye. What is the nature and power of the lens required to correct the problem?

Given: The far point of a myopic person is 80 cm in front of the eye.

To: To find the nature and power of the lens required to correct the problem.

The person is suffering from myopia. And this person needs a concave lens to correct the defect. The lens should be such that an object at infinity must form its image at the far point of $80\ cm$ to make it visible to the myopic person.

The power of the lens can be obtained as:

$\boxed{P=\frac{1}{f}}$

$P\rightarrow$ Power of the lens

$f\rightarrow$ focal length of the lens

It is given, $f=-80\ cm=-0.8\ m$

​

$P=\frac{1}{-0.8\ m}$

​

$=-1.25\ D$

Therefore, 

Power of the lens:
The power of the lens is $-1.25\ D$.

$(-ve)$ sign implies that it is a concave lens. It is diverging in nature.