The focal length of a lens is +150 mm. What kind of lens is it and what is its power?

Given:

Focal length, $f$ = $+$150 mm = $+$0.15 m

To find: Kind of lens and its power, $P$.

Solution:

Power of a lens is given by:

$P=\frac {1}{f}$

Substituting the given values we get-

$P=\frac {1}{0.15}$

$P=\frac {100}{15}$

$P=+6.66D$

Thus, the power of the lens $P$ is 6.66 D, and the positive sign $(+)$ implies that the lens is convex in nature. 

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Updated on: 10-Oct-2022

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