States of Matter
Why is a normal eye not able to see clearly the objects placed closer than 25 cm?
Ciliary muscles contract and expand to change the focal length of eye lens so that it is able to see objects at variable distances. However, too much contraction lays a lot of stress on the eye muscles and when objects are closer than the near point(25 cm), the eye is unable to focus its image on retina. Hence, a normal eye cannot see objects closer than 25 cm clearly.