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The power of lens is 2.5 D. What is its ...

The power of lens is `2.5 D`. What is its focal length ?

A

`+25` cm

B

`20` cm

C

`+40` cm

D

`-10` cm

Text Solution

Verified by Experts

The correct Answer is:
C
The power of this lens has positive sign, so it is a convex lens. Now,
Power, P`=1/("f in metres)`
So, `+2.5=1/f`
and `f-1/2.5`m
`=1/2.5 xx 100` cm
So, Focal length, f=40cm (or `+40` cm)
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