This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Types of Errors of Refraction, Subject name: Ophthalmology
Diopteric power is related - 
Select and explain. 
A. Directly to square of focal length, B. Inversely to focal length, C. Directly to focal length, D. Inversely to square of focal length
B: Inversely to focal length
Answer: B: Inversely to focal length 
Explanation: Ans. is 'b' i.e. Inversely to focal length Optical powero Optical power (also referred to as dioptric power, refractive power, focusing power, or convergence power) is the degree to which a lens, mirror, or other optical system converges or diverges light. It is equal to the reciprocal of the focal length of the device: P = 1/f. High optical power corresponds to short focal length. The SI unit for optical power is the inverse metre (m 1), which is commonly called the dioptreo Converging lenses have positive optical power, while diverging lenses have negative power. When a lens is immersed in a refractive medium, its optical power and focal length change.