Question

With the help of cilliary muscles the human eye can change the curvature and thus alter the focal length of it's len's. State the changes that occur in the curvature and focal point length of the eye lens while viewing 1) a distance object 2) nearby object.Why a normal eye is not able to see distinctly the objects placed closen than 25 cm without putting strain on the eye?

Answer 1

1) Ciliary muscles stretch and the lens becomes thin so focal length increases.

2) Ciliary muscles relax so lens becomes thicker , thus decreasing the focal length