How We See?
Formation of Image
The cornea refracts the light rays entering the eye through the pupil and converges them through the lens.
The ciliary muscles attached to the lens help adjust it's thickness (in effect the focal length)
As the lens shape changes, it focuses light on the retina.
The light stimulates photoreceptors and nerve impulses and the optic nerve to the brain.
The brain interprets the impulses and you are able to see.
At times the lens is not able to form an image on the retina directly, leading to vision defect.
Some people can see nearby objects clearly but distant objects appear hazy.
This defect is called nearsightedness or myopia.
Some people can see distant objects clearly but nearby objects appear blurred.
This defect is called farsightedness or hyperopia.
For correction of these defects we use external lenses so that the light is converged on the retina each time.
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