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प्रश्न
Differentiate between myopia and hypermetropia. What type of spectacles should be worn by a person having the defects of myopia as well as hypermetropia? How does it help?
उत्तर
| Sl. no. | Myopia (short-sightedness) |
Hypermetropia (long-sightedness) |
| 1 | A defect of vision because of which a person cannot see distant objects clearly. | A defect of vision because of which a person cannot see nearby objects clearly. |
| 2 | The far point of a myopic eye is closer than infinity. | The near point of a hypermetropic eye is more than 25 cm away. |
| 3 | Myopia occurs because the eye lens has a high converging power or because the eye ball is too long. | Hypermetropia occurs because the eye lens has a low converging power or because the eye ball is too short. |
| 4 | A person suffering from myopia should wear spectacles with concave lenses as a concave lens decreases the converging power of the eye lens and therefore helps in forming the images of faraway objects on the retina of the myopic eye. | A person suffering from hypermetropia should wear spectacles with convex lenses as a convex lens increases the converging power of the eye lens and therefore helps in forming the images of nearby objects on the retina of the hypermetropic eye. |
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संबंधित प्रश्न
Name the defect of vision which makes the eye-lens cloudy resulting in blurred vision.
Though a woman can see the distant object clearly, she cannot see the nearby objects clearly. She is suffering from the defect of vision called:
(a) long-sight
(b) short-sight
(c) hind-sight
(d) mid-sight
A person can read a book clearly only if he holds it at an arm's length from him. Name the defect of vision:
if the person is an old man
A person can read a book clearly only if he holds it at an arm's length from him. Name the defect of vision:
if the person is a young man
List two causes of presbyopia. Draw labelled diagram of a lens used for the correction of this defect of vision.
Give Technical Term:
The path which responsible for protecting the eye from sweat.
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.
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.
