A thin lens has a focal length $- 25 c m$ . Calculate the power of lens in dioptre.
-4

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Solution

The correct option is A -4
Given:
The focal length of a lens is
$f = - 25 c m = \frac{- 25}{100} m = - 0.25 m$
The power of the lens is given by
$P = \frac{1}{f (in metre)}$
$P = \frac{1}{- 0.25 m}$
$P = - 4 D$

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A thin lens has a focal length −25 cm. Calculate the power of lens in dioptre.-4

The correct option is A -4Given: The focal length of a lens is f=−25 cm=−25100 m=−0.25 m The power of the lens is given by P=1f(in metre) P=1−0.25 m P=−4D

A thin lens has a focal length $- 25 c m$ . Calculate the power of lens in dioptre.
-4

The correct option is A -4
Given:
The focal length of a lens is
$f = - 25 c m = \frac{- 25}{100} m = - 0.25 m$
The power of the lens is given by
$P = \frac{1}{f (in metre)}$
$P = \frac{1}{- 0.25 m}$
$P = - 4 D$