Posted by crystal on .
A certain person's eye measures 24.0 mm from the pupil to retina.
(a) If we treat the eye's lens as a thin lens, what is its focal length when the person focuses on a pencil 44.3 cm from the eye?
(b) While the person focuses on the pencil, what is the image distance for a wall 426 cm from the eye?

college physics 
drwls,
(1) 1/2.4 + 1/44.3 = 1/f
Solve for for in cm.
(2) Using the same f that you get in (1), solve
1/x + 1/426 = 1/f
to get the value of the wall image distance, x.
It will be in centimeters.