Power of a lens of focal length 25 {cm} is

Correct Answer is : + 4 Dioptre

Correct Answer is : + 4 Dioptre

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UPSC NDA 2 2021 General Ability Solved Paper

Question : 112 of 150

Marks: +1, -0

\mathrm{cm}

Solution:

25\ \mathrm{cm}

is +4 Dioptre.

First we will convert the focal length in meters.

\Rightarrow \;\; 25\ \mathrm{cm}=0.25\ \mathrm{m}

Now, substituting the value of focal length in the formula of power of lens we

\mathrm{m}^{-1}

is also expressed as diopters or

D

As it is a convex lens so its power is positive. Thus, the power of the lens is

+4 D

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