Solutions: Medical Option - the EYE
A lens is used as shown in the diagram to enable a person with an eye defect to see distant objects clearly.
(i) Name the defect corrected by this lens.
Short sight [myopia]
(ii) Determine the power of the lens.
u = infinity so 1/u = 0
v = - 0.50 m
P = 1/f = 1/u + 1/v
P = 0 - 1/0.50 = - 2.0 D (must be negative!)
(iii) Draw a ray diagram to show the path through the eye of rays from a distant object when a correcting lens is not being used.
Rays cross in front of retina from parallel incident rays
(iv) Draw a ray diagram to show the path through the eye of rays from an object positioned at the uncorrected far-point.
Image on retina, object at uncorrected far point
(Total 5 marks)