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प्रश्न
A person is unable to see clearly a poster fixed on a distant wall. He however sees it clearly when standing at a distance of about 2 m from the wall.
- Draw ray diagram to show the formation of image by his eye lens when he is far away from the wall.
- List two possible reasons of this defect of vision.
- Draw ray diagram to show the correction of this defect using appropriate lens.
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उत्तर
(a)
Myopic eye
(b) In a myopic eye, rather than at the retina itself, the image of a distant object is created in front of the retina. This flaw may result from (i) an excessively curved eye lens or (ii) an elongated eyeball. With the use of a concave lens of the appropriate power, this flaw can be fixed. The flaw is fixed by returning the picture to the retina with a concave lens of the proper power.
(c)
Correction for myopic
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संबंधित प्रश्न
A person with a myopic eye cannot see objects beyond 1.2 m distinctly. What should be the type of the corrective lens used to restore proper vision?
The far point of a myopic person is 80 cm in front of the eye. What is the nature and power of the lens required to correct the problem?
A student suffering from myopia is not able to see distinctly the objects placed beyond 5 m. List two possible reasons due to which this defect of vision may have arisen. With the help of ray diagrams, explain
(i) why the student is unable to see distinctly the objects placed beyond 5 m from his eyes.
(ii) the type of the corrective lens used to restore proper vision and how this defect is corrected by the use of this lens.
(b) If, in this case, the numerical value of the focal length of the corrective lens is 5 m, find the power of the lens as per the new Cartesian sign convention
The kind of lens required to correct Myopia
Differentiate between myopia and hypermetropia.
A person cannot see the distant objects clearly (though he can see the nearby objects clearly). He is suffering from the defect of vision called:
(a) cataract
(b) hypermetropia
(c) myopia
(d) presbyopia
A short-sighted person has a near point of 15 cm and a far point of 40 cm.
(a) Can he see clearly an object at a distance of:
(i) 5 cm?
(ii) 25 cm?
(iii) 50 cm?
(b) To see clearly an object at infinity, what kind of spectacle lenses does he need?
State one role of ciliary muscles in the human eye.
Distinguish between the following pair of words:
Myopia and hypermetropia
Give Reason:
Deficiency of vitamin A causes night blindness.
