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Numerical

If focal length of a convex lens is 20 cm at what is the power of the lens?

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#### Solution

**Given:** Focal length (f ) = 20 cm = 0.2 m

**To find:** Power of the lens (P)

**Formula:** P = `1/("f"("m"))`

**Calculation:** From formula, P = `1/0.2` = 5 D

The power of the convex lens is **5 D**.

Concept: Power of a Lens

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