Question

The ciliary muscles of a normal eye are in their:
(i) most relaxed state (ii) most contracted state
(a) In which of the two cases is the focal length of the eye-lens more?
(b) In which of the two cases is the power of the eye-lens more?
​Give reason for your answer.

Answer 1

(a) The focal length of the eye lens is more when the ciliary muscles of a normal eye are in their most relaxed state. In this state the lens becomes thin.

(b) As the power of a lens is inversely proportional to its focal length. Hence, the power of the eye lens would be more when the focal length would be minimum, which happens when ciliary muscles are in the most contracted state. In this case, the lens becomes thick.