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प्रश्न
State reasons for Myopia. With the help of ray diagrams, show the:
- image formation by a myopic eye, and
- correction of myopia using an appropriate lens.
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उत्तर
Myopia is a visual impairment in which a person can see all around objects clearly, but finds it difficult to comfortably focus on a single object. This eye is referred to as the myopia eye.
Myopia can be caused by:
- increase in curvature of the lens.
- increase in the length of the eye ball.
(a) A myopic eye's far point is close to that infinite distance. In front of the retina, it creates the separate object image depicted in the figure.
(b) Concave lens has an ability to diverge incoming rays, it is used to correct this defect of vision. The image is allowed to form at the retina by using a concave lens of suitable power as shown in the figure.
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संबंधित प्रश्न
An eye has a near point distance of 0.75 m. What sort of lens in spectacles would be needed to reduce the near point distance to 0.25 m? Also calculate the power of lens required. Is this eye long-sighted or short-sighted?
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
To read a book held at a distance of 25 cm, will she need converging or diverging spectacle lenses?
Name the following:
The eye defect caused due to shortening of the eye ball from front to back.
Have a look at the posture of this girl who is reading a book and answer the questions which follow:
Name the problem she is facing.
The near point of the eye of a person is 50 cm. Find the nature and power of the corrective lens required by the person to enable him to see clearly the objects placed at 25 cm from the eye?
Differentiate between:
Short-sightedness and Long-sightedness.
Study the following diagram carefully and then answer the questions that follow. The diagram is depicting a defect of the human eye :
(i) Identify the defect shown in the diagram.
(ii) Give two possible reasons for the above defect.
A person cannot see distinctly objects kept beyond 2 m. This defect can be corrected by using a lens of power:
Observe the following diagram and answer questions following it:
- Identify the defect of vision shown.
- List its two causes.
- Name the type of lens used for the correction of this defect.
