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  • Explain the structure and functioning of Human eye. How are we able to see nearby as well as distant objects?

Explain the structure and functioning of Human eye. How are we able to see nearby as well as distant objects?

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Structure of eye:

Cornea is transparent. It is responsible for most of the refraction of light rays towards the retina.
Iris is a dark, circular muscular diaphragm behind the cornea.
It controls the pupil size which in turn controls the amount of light entering the eye.
Pupil is surrounded by the iris. It regulates and controls the amount of light entering the eye.
Retina is the innermost layer of the eye. It contains an outer pigmented layer and an inner nervous layer which contains the photo receptors (rods
and cones).
Cone cells are coned shaped cells which detect colour
Rod cells are rod shaped cells which are light sensitive.
Optic nerve connects the eye to the brain.
Nerve fibres carry impulses from the retina to the visual cortex.
Eye lens is made up of a fibrous, jelly-like material. It is transparent and has biconvex structure. It forms an inverted real image of the object on
the retina and also separates the aqueous and the vitreous humours.
Vitreous humour is clear, semi-solid supporting the eye ball
Human eye has an eye lens to adjust its focal length. This is known as power of accommodation.
We are able to see nearby and also the distant objects clearly due to this power of accommodation of the eye.
When the muscles are relaxed, the lens becomes thin and its focal length increases.
When the muscles are contracted, the lens becomes thick and its focal length decreases.
This enables us to see the distant as well as nearby objects clearly.
This is what makes eye to see different objects at different distances clearly.

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