When looking at objects various distances away from you, your eye must create an image at the back of itself (at the retina). since your eye does not change size when looking to different dis tances, you must change the shape of the lens located at the front of your eye to make a clear image of different object distances at the same image distance. your near point is the shortest distance from the lens in your eye to an object for which you can make a clear image on your retina. a human with good vision will have a near point of 25 cm. the average eye length from front to back is 24 mm. assume that your lens is at the front of your eye, the lens is a spherical thin lens, and that your eye is made of air except for the lens. a) when looking at an object placed at her near point, what is the focal length of an average hu- man's lens? b) what is the focal length of her lens when looking at the moon? (hint: the moon is really far away) c) hyperopia occurs when your eye is too short. the lens is still limited to the same range curvatures. if somebody has an eye length of only 23 mm, what is their near point? d) you are an eye doctor in charge of prescribing glasses for this hyperopic person. if glasses rest 2.5 cm from the eye, what focal length should you prescribe to correct their near point?