Question

A nearsighted person cannot clearly see beyond 200 cm. Find the power of the lens needed to see objects at large distances.

Answer 1

Given :

For a near-sighted person, u = ∞.

v = – 200 cm = – 2 m

The lens formula is given by

1/v-1/u=1/f

On putting the respective values, we get:

1/f=1/-2-1/∞

=-12

∴ Power of the lens = 1/f= – 0.5 D

Answer 2

Hey !!

Question

A nearsighted person cannot clearly see beyond 200 cm. Find the power of the lens needed to see objects at large distances.

ANSWER

Given data,

v = -200 cm

         = 2 m

Apply the lens formula

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

Subsituting the values, we get

$\frac{1}{f} = \frac{1}{-2}  - \frac{1}{infinity}$

 → -12

Now, power of the lens

$\frac{1}{f} = -0.5 D$

NOTE :- Near-sighted (u) = ∞

GOOD LUCK !!