How the human eyes work

When we look at an object, light rays from each point of the object enter our eyes. As they pass through the cornea,aqueous humour, lens and vitreous humour,they are bent(refracted) and brought to a focus on the retina to form an image. This image is real,inverted and smaller than the object. Light rays are bent most at the air/cornea surface. The lens makes the final fine bending adjustments needed to focus the rays on the retina.
Each point of light that falls on the retina to form the image stimulates the rods and cones in that region.A pattern of electrical impulses is sent to the brain which interprets it,drawing on past experience. The brain tells us that the object is upright and gives us its real size and distance from the eye. We,therefore, see the object as it actually is,and not as the image formed on the retina. We see an object most clearly when its image falls on the fovea centralis which is along the optical (principal) axis of the eye lens.

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