<prompt> The focal length of the lens is 075 m, what will be its refractive power -0.75D1.5D1.33 D1.25 D  <response>: 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 1f, The unit of power is dioptre D. One dioptre is the power of a lens of focal length one metre. 