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प्रश्न
Differentiate the eye defects: Myopia and Hypermetropia
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
What is myopia?
List three common refractive defects of vision. Suggest the way of correcting these defects.
Name the defect of vision in which the eye-lens loses its power of accommodation due to old age.
A student sitting in the last row of the class-room is not able to read clearly the writing on the blackboard.
How can this defect by corrected?
What is long-sightedness? State the two causes of long-sightedness (or hypermetropia). With the help of ray diagrams, show:
(i) the eye-defect long-sightedness.
(ii) correction of long-sightedness by using a lens.
Name the following:
The photosensitive pigment present in the rods of the retina.
Name the following:
The eye defect caused due to shortening of the eye ball from front to back.
Give Reason:
Older people require glasses to read and write.
A student sitting at the back of the classroom cannot read clearly the letters written on the blackboard. What advice will a doctor give to her? Draw ray diagram for the correction of this defect.
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.
