Question

Q-10 What is the power of lens? Write SI Unit of power of lens and Write the EquationShowing relation between power of lens and focal length.




give long answer of 3 marks
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Answer 1

Answer:

If a lens has a shorter focal length it is said to be more powerful. The power of a lens is defined as the reciprocal of the focal length. Lens power is measured in dioptres (D).

powerofalens(D)=1focallength(m)

P=1f

Converging (convex) lenses have positive focal lengths, so they also have positive power values.

Diverging (concave) lenses have negative focal lengths, so they also have negative power values.

Answer 2

The power of a lens is defined as the reciprocal of the focal length.

The S.I. unit of power of lens is dioptre (D)

The power of a lens is defined as the reciprocal of its focal length in meters, or D = 1/f, where D is the power in diopters and f is the focal length in meters.