A lens has power of, -25 D. What is the focal length and nature of the lens?

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Solution

We know that power of lens is $P = \frac{1}{f}$
P=-25D
So $- 25 = \frac{1}{f}$
$f = - .04 m = - 4 c m$
The power of this lens has minus sign, so it is a concave lens.

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A lens has power of, -25 D. What is the focal length and nature of the lens?

We know that power of lens is P=1fP=-25DSo −25=1ff=−.04m=−4cmThe power of this lens has minus sign, so it is a concave lens.

We know that power of lens is $P = \frac{1}{f}$
P=-25D
So $- 25 = \frac{1}{f}$
$f = - .04 m = - 4 c m$
The power of this lens has minus sign, so it is a concave lens.