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

For a near-sighted person, u = ∞.
Now, we have:

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/∞ =-1/2`

∴ The power of the lens = `1/f`= -0.5 D