Answer :
Final answer:
A myopic person with a far point of 40 cm requires a lens with a focal length of -40 cm and a power of -2.5 diopters to see distant objects clearly. The correct answer is option: A. -40 cm, -2.5 D
Explanation:
The question concerns the focal length and power of a corrective lens for a person with myopia, or nearsightedness. If the far point of the person is 40 cm, a diverging lens is needed to correct their vision for distant objects.
The focal length of the needed lens must match the far point for it to form an image at infinity for distant objects. The power P of a lens in diopters (D) is given by P = -1/f (in meters).
Therefore, if the focal length f is -40 cm, which is -0.40 meters, the power P would be -1/(-0.40) = +2.5 D. Thus, the lens must have a focal length of -40 cm and a power of -2.5 D.
