This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Optics and refraction, Subject name: Ophthalmology
[{'content': 'Focal length of lens is 0.75 m, what will be its refractive power - \nSelect and explain. \nA. 0.75D, B. 1.5D, C. 1.25 D, D. 1.33 D', 'role': 'user'}, {'content': 'Answer: D \nExplanation: 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. Reference : A K KHURANA OPHTALMOLOGY,Edition 4, page-23', 'role': 'assistant'}]