Question

The far point of a myopic eye is 20 cm . Find the power of his lens used.

• A. 3D
• B. -3D
• C. 5D
• D. -5D

Answer 1

The correct option is D

-5D

Lens formula:

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

u = - infinity

v = - 20 cm

$\frac{1}{f}$ = $\frac{-1}{20}$

f = -20 cm or $\frac{-1}{5}$ m

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

P = -5D