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प्रश्न
Differentiate the eye defects: Myopia and Hypermetropia
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उत्तर
| Myopia | Hypermetropia |
| Myopia, also known as short-sightedness, occurs due to the lengthening of the eyeball. | Hypermetropia, also known as long-sightedness, occurs due to the shortening of the eyeball. |
| With this defect, nearby objects can be seen clearly but distant objects cannot be seen clearly. | With this defect, distant objects can be seen clearly but nearby objects cannot be seen clearly. |
| The focal length of the eye lens is reduced or the distance between the eye lens and retina increases. | The focal length of the eye lens is increased or the distance between the eye lens and retina decreases. |
| The far point will not be infinity for such eyes and the far point has come closer. | Hence, the near point will not be at 25 cm for such eyes and the near point has moved farther. |
| Due to this, the image of distant objects is formed before the retina. | Due to this, the image of nearby objects is formed behind the retina. |
| This defect can be corrected using a concave lens | This defect can be corrected using a convex lens. |
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संबंधित प्रश्न
Explain two possible reasons of myopia. How can it be corrected? Explain with a suitable diagram.
Explain with the help of labelled ray diagram, the defect of vision called myopia and how it is corrected by a lens.
What is meant by optical illusion? Give one example.
Select the odd one in the following series:
Endolymph, Tympanic membrane, Semi-circular canal, Blind spot.
Write whether the following is true or false:
A convex lens is used for correcting myopia.
Rewrite the following table so as to match second and third column with first column.
|
Column I
|
Column II
|
Column III
|
|
(i) Myopia
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Old age problem
|
Bifocal lens
|
|
(ii) Presbyopia
|
Nearsightedness
|
Concave lens.
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Name the following:
The defect of the human eye caused due to the uneven surface of the cornea.
Assertion: Concave mirrors are used as reflectors in torches, vehicle head lights and in search lights.
Reason: When an object is placed beyond the center of curvature of a concave mirror, the image formed is real and inverted.
Observe the figure and answer the following questions:
- Name the defect of vision represented in the above figure.
- State the reasons for this defect.
- How is it corrected?
- Draw the diagram to show the correction of this defect.
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.
