Presbyopia is the tendency to gradually become far-sighted (hyperopic) as you age. If you have normal vision when you are young, you have a near point of 25 cm. A. If the distance between your eye's lens and retina is1.75cm, what is the focal length of your eye's lens when you look at an object at your near point? f= cm B. As you get older, suppose that the near point of your eye increases to50cm. What is the focal length of your eye's lens when you look at an object at your near point now? f= cm C. With your near point at50cm, what is the focal length of the corrective lens (placed directly in front of your eye's lens) which you would need to look at an object that is 25 cm in front of your eye? f= cm D. As you continue to age, the corrective lenses will no longer be sufficient to allow you to see an object that is 25 cm in front of your eye. When you are wearing your corrective lenses, suppose that you can now see objects only if they are no closer than38cm in front of your eye. What is the actual near point of your eye now? N= cm What is the focal length of your eye's lens that corresponds to this new near point? f= cm

. since the near point increases to 50 cm it means that the image forms at a minimum distance of gocm. distance of image = di= - 50cm distance of object = do = - 25(m from Leng Formula we have I - di do 50 50 $ 25 1 - 1+2 50 50 = 50 (m focal length of the ex lens = = 50cm. D) For anormal vision, the near point is 25 cm Due to aging objects closed up to 38 cm are visible. This the actual mead point of eye will be 38 cm For focal length of the eyes distance of image - di= - 38cm distance of object = 06 : - 25cm - 25+ 38 38 -( - 25 ) - 38 + 25 - 25 x38 13 950 P = ) 950 13 - 73.076 (m f= 73.1cm Focal length of the eye long= 73.1 cm