Human eye and working of its lens.
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Answers
Answer:
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Explanation:
The lens focuses light through the vitreous humor, a clear gel-like substance that fills the back of the eye and supports the retina. The retina receives the image that the cornea focuses through the eye's internal lens and transforms this image into electrical impulses that are carried by the optic nerve to the brain.
Answer:
The human eye is one of the most sensitive sense organs of sight which enables us to see the wonderful world of light and colour around us. It is like a camera having la lens system and forming an inverted, real image on a light sensitive screen inside the eye. The structure and working of the eye is as follows :
Structure and Working of Human Eye
The human eye has the following parts :
(i) Cornea : It is the transparent spherical membrane covering the front of the eye.
(ii) Iris : It is the coloured diaphragm between the cornea and lens.
(iii) Pupil : It is the small hole is the iris.
(iv) Eye lens : it is a transparent lens made of jelly like material.
(v) Ciliary muscles : These muscles hold the lens in positions.
(vi) Retina : it is the back surface of the eye.
(vii) Blind spot : it is the point at which the optic nerve leaves the eye. An image formed at this point is not sent to the brain.
(viii) Aqueous humor : It is clear liquid region between the cornea and the lens.
(ix) Vitreous humor : The space between eye lens and retina is filled with another liquid called vitreous humor.
In the eye, the image is formed on the retina by successive refractions at the cornera, the aqueous humor, the lens and the vitreous humor. Electrical signals then travel along the optic nerve to the brain to be interpreted. In good light, the yellow spot is most sensitive to detail and the image is automatically formed there.
Chapter-wise important notes science (Physics) for Board Exams
Power of Accommodation
The image of the objects at different distances from the eye are brought to focus on the retina by changing the focal length of the eye-lens, which is composed of fibrous jelly-like material, can be modified to some extent by the ciliary muscles.
Near Point and Far Point
The nearest point at which a small object can be seen distinctly by the eye is called the near point. For a normal eye, it is about 25 cm and is denoted by the symbol D.
With advancing age, the power of accommodation of the eye decreases at the eye lens gradually loses its flexibility. For most of the old persons aged nearly 60 years, the near point is about 200 cm and corrective glasses are needed to see the nearby objects clearly.
The farthest point upto which our eye can seen objects clearly, without any strain on the eye is called the far point. For a person with normal vision, the far point is at infinity.
Least Distance of Distinct Vision
The minimum distance of an object from the eye at which it can be seen most clearly and distinctly without any strain on the eye, is called the least distance of distance of distinct vision. For a person with normal vision, it is about 25 cm and is represented by the symbol D, i.e.
least distance of distinct vision = D = 25 cm.