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प्रश्न
List two causes of presbyopia. Draw labelled diagram of a lens used for the correction of this defect of vision.
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उत्तर
Causes of presbyopia :
Aging
Weakening of ciliary muscles
It is treated by using a bifocal lens both concave and convex.
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संबंधित प्रश्न
What is the far point and near point of the human eye with normal vision?
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
Name the defect of vision in a person:
whose near point is more than 25 on away.
What is the scientific name of
long-sightedness?
Where is the near point of a person suffering from hypermetropia (or long-sightedness)?
A person is unable to read a book placed closer than 1 meter from his eyes. Identify the defect of vision in his eyes. Draw the ray diagrams to show the defect of vision and its correction.
A person is unable to see objects distinctly placed within 50 cm from his eyes.
(a) Name the defect of vision the person is suffering from and list its two possible causes.
(b) Draw a ray diagram to show the defect in the above case.
(c) Mention the type of lens used by him for the correction of the defect and calculate its power. Assume that the near point for the normal eye is 25 cm.
(d) Draw a labeled diagram for the correction of the defect in the above case.
In what two whys is a yellow spot different from the blind spot?
Draw a neat labeled diagram to show how hypermetropia can be rectified.
Given alongside is a diagram depicting a defect of the human eye. Study the same and answer the questions that follow:
 |
- Name the defect shown in the diagram.
- Give two possible reasons for this defect.
- Name the parts labelled 1 to 4.
- Name the type of lens used to correct this eye defect.
- Draw a labelled diagram to show how the above mentioned defect is rectified using the lens named above.
