What is the unit of measurement for optical power of the lens?

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Accepted Answer

Definition:

- Optical power $P$ of a lens is defined as the reciprocal of its focal length $f$ (measured in meters):

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

- The SI unit of optical power is the diopter (symbol D), where $1\ 	ext{D} = 1\ 	ext{m}^{-1}$. Example: a lens with $f=0.5\ 	ext{m}$ has $P=2\ 	ext{D}$.

Why other options are wrong:

- Yotta: an SI prefix ($10^{24}$), not a unit of optical power.
- Katal: unit of catalytic activity, unrelated to optics.
- Radian: unit of angle, not lens power.

Therefore the correct choice is (4) Diopter.

FINAL_ANSWER: d

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