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

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#### Solution

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

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