Question

Bill is farsighted and has a near point located 119 cm from his eyes. Anne is also farsighted, but her near point is 70.0 cm from her eyes. Both have glasses that correct their vision to a normal near point (25.0 cm from the eyes), and both wear glasses 2.0 cm from the eyes. Relative to the eyes, what is the closet object that can be seen clearly in the following situations.

(a) Anne when she wears Bill's glasses
(b) Bill when he wears Anne's glasses

Answer 1

Step-by-step explanation:

For Bill's glasses)

d_o=25 cm-2 cm=23.2 cm

d_i=129 cm-2 cm=127 cm

We know that

`1 / f = 1 / d_o + 1 / d_i`

`f=(1 / d_o + 1 / d_i)^-1`

so plug the numbers in

`f = (1 / (23) + 1 / (127))^-1`

= 28.08 cm

For Anna's glasses)

d_o=25 cm-2 cm=23 cm

d_i=70.0 cm-2 cm=68 cm

Same thing

`(1 / f = 1 / d_o + 1 / d_i )`

`f=(1 / do + 1 / di)^-1`

so plug the numbers in

`f = (1 / (23) + 1 / (68))^-1`

= 17.21 cm