how do you know if the far point is the object distance (So) or the image distance (Si) in a problem? For example: Sam purchases +3.2 diopter eyeglasses which corrects his faulty vision to put his near point at 25 cm. (Assume he wears the lenses 2.0 cm from his eyes).
(a) Is Sam nearsighted or farsighted?
(b) Calculate the focal length of Sam's glasses.
(c) Calculate Sam's near point without glasses.
(d) Pam, who has normal vision with near point at 25 cm, puts on Sam's glasses. Calculate Pam's near point with Sam's glasses on.