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

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-3D

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-5D

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Solution

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

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

The correct option is D -5D Lens formula: 1v - 1u = 1f u = - infinity v = - 20 cm 1f = −120 f = -20 cm or −15 m Power = 1f P = -5D

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