Question

the focus lenght of convex lens is 40cm .
calculte the powel of lens.
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Answer 1

Explanation:

P=1/f

As it is convex lens then it's focus would be positive

F=40cm

F= 40/100 m

F= 0.4m

P=1/0.4

P=10/4

P=5/2

P=2.5D