$(a)$ Explain how a normal human eye is able to see distinctly objects placed at a distance as well as those placed at a nearer distance.
$(b)$ What are the far point and near point of a normal human eye?

(N/A) The ciliary muscles change the curvature of the eye lens as per the requirement of the eye. This process changes the focal length of the eye lens,which is known as accommodation.
When the ciliary muscles are relaxed,the lens becomes thin,increasing its focal length,which allows the eye to see distant objects clearly.
When viewing closer objects,the ciliary muscles contract,which makes the eye lens thicker and decreases its focal length,allowing the eye to focus on near objects.
$(b)$ The far point of a normal human eye is at infinity,and the near point is at $25\, cm$ from the eye.