Question

a lens is of focal length 20 cm . what is its power ?

Answer 1

HEY MATE HERE IS YOUR ANSWER....
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$1 \: metre = 100cm. \\ 20cm = \frac{20}{100}m \\ = > 0.2m. \\ as \: we \: know. \\ power(P) = \frac{1}{focal \: length(in \: metre)} \\P = \frac{1}{0.2} \\ P = \frac{10}{2} \\ P = 5 \: diaopter.$
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HOPE IT HELPS YOU.....

Answer 2

$\red{Hey mate}$

Here is your answer!!

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FOCAL LENGTH,

f = 40 cm

power (P) = 100 / f(cm)

= 100 / 20

= 5 D

the power of the lens is 5D.

be brainly