Question

how to find the power of lens ,having 40 cm focal lenght ??

Answer 1

by appyling the formula P=1/f
P= 100/40
P=2.5cm
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Answer 2

✔✔HEY MATE HERE IS UR ANSWER ... ✔✔
As we the formula of the power is
P = 1/f
P=power ; F = focal length in metres..
We have,
f = 40 cm
= 40cm/100cm (convert cm into m )
= 0.4 m

Now,
P = 1/f
= 1/ 0.4
= 10/4

P = 2.5 D

I hope it helps......