Question

the far point of a myopic person is 80 cm in front of the eye. What is the nature and the power of lens required to enable him to see very distant objects clearly?

Answer 1

The nature and the power of lens required to enable him to see very distant objects clearly is concave lens with -1.25 D.

Explanation:

For person affected with myopic condition, the image instead of forming on retina, it forms in front of it. In order to cure such type of defect, concave lens is used.  

To calculate the power of the lens, focal length is required. From the given condition it can be understood that focal length is calculated from the distance of far point form the eye which is 80 cm. Hence, focal length is calculated as -80 cm or -0.8 m.

When this value is substituted in the following formula, the power can be calculated:

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

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

$P=-1.25 \ D$

Answer 2

• f=80 cm convert into meter that is 0.8m
• f=80 cm convert into meter that is 0.8mp=1/f
• f=80 cm convert into meter that is 0.8mp=1/fp=1/0.8
• f=80 cm convert into meter that is 0.8mp=1/fp=1/0.8p=1.25 diopter