Light enters theeye through thecornea and thelens. It is focusedonto the retina bythe ciliarymuscles, whichchange the shapeof the lens.
The eye produces a real, invertedimage on the retina.
(a)When the eye is viewing a distant object the ciliary muscles are relaxed and the focal length of the lens is at its greatest.(b)When the eye is focusing on a near object the ciliary muscles are tensed, changing the shape and reducing the focal length of the lens.
Cilliary muscles pullon lens. This causes itTo change shape.From the lens-makersformula this changesthe focal lengthof the lens.We see objects atdifferent distanceby changing theshape of our eyelens.ACCOMODATION
Images in the human eyeIn the human eye, a real, inverted image is formed ona light-sensitive surface, called the retina.Accommodation is the process by which the focal lengthof the eye is automatically adjusted , so that objectsat different distance produce focused images on theretina.Near pointThe near point of the eye is the point nearest the eyeat which an object can be placed and still have asharp image produced on the retina. For a normal eye,the near point is located 25cm from the eye.Far pointThe far point of the eye is the location of thefarthest object on which the fully relaxed eye canfocus. For a normal eye, the far point is located atinfinity.