Two lab partners, Mary and Paul are both farsighted. Mary has a near point of 6.3 cm from her eyes and Paul has a near point of 124 cm from his eyes. Both students wear glasses that correct their vision to a normal near point of 25.0 cm from their eyes, and both wear glasses 1.80 cm from their eyes. In the process of wrapping up their lab work and leaving for their next class, they get their glasses exchanged (Mary leaves with Paul's glasses and Paul leaves with Mary's glasses). When they get to their next class, find the following.
(a) Determine the closest object that Mary can see clearly (relative to her eyes) while wearing Paul's glasses in meters.
(b) Determine the closest object that Paul can see clearly (relative to his eyes) while wearing Mary's glasses in meters.
Here are two hints I got:
Try splitting the problem into two steps. First, find the refractive power of each pair of glasses and then the closest object that each student can clearly view while wearing the other student's glasses. Think carefully about whether a particular object or image distance should be relative to the glasses or relative to the eyes. Give careful thought to the appropriate algebraic sign (±) for all object and image distances
How can you modify the result used to determine the closest object Mary can see clearly to determine the closest object Paul can see clearly?