The focal length of a convex lens is 25 cm. What is its power?

Given: 

Focal length, $f$ = $+$25 cm = $+$0.25 m  $(\because lens\ is\ convex\ in\ nature,\ focal\ length\ will\ be\ positive)$

To find: ​​Power of a lens, $P$.

Solution:

We know that power of the lens is given by-

$Power\ (P)=\frac {1}{f}$

Substituting the given value we get-

 $P=\frac {1}{0.25}$

 $P=\frac {100}{25}$

 $P=+4D$

Hence, the power of the lens is 4 D.

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Updated on: 10-Oct-2022

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