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What is The focal length of the lens is 0*75 m, what will be its refractive power - and explain in detail?
The focal length (f) of a lens is the distance between the optical centre and the principal focus.
Power of a lens (P) is defined as the ability of the lens to converge a beam of light falling on the lens.
It is measured as reciprocal of the focal length in metres i.e. P = 1/f, The unit of power is dioptre (D). One dioptre is the power of a lens of focal length one metre.