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प्रश्न
What are the two most common defects of vision (or defects of eye)? How are they corrected?
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उत्तर
The two most common defects of vision (or defects of the eye) are the following.
1. Myopia (short-sightedness or near-sightedness): Myopia is an eye defect because of which a person cannot see faraway objects clearly but can see nearby objects normally. By using spectacles with concave lenses, myopia can be corrected, as a concave lens reduces the converging power of the eye lens and therefore forms the images of faraway objects on the retina of the myopic eye.
2. Hypermetropia (long-sightedness or far-sightedness): Hypermetropia is an eye defect because of which a person cannot see nearby objects clearly but can see faraway objects normally. By using spectacles with convex lenses, hypermetropia can be corrected, as a convex lens increases the converging power of the eye lens and therefore forms the images of nearby objects on the retina of the hypermetropic eye.
The two most common defects of vision (or defects of the eye) are the following.
1. Myopia (short-sightedness or near-sightedness): Myopia is an eye defect because of which a person cannot see faraway objects clearly but can see nearby objects normally. By using spectacles with concave lenses, myopia can be corrected, as a concave lens reduces the converging power of the eye lens and therefore forms the images of faraway objects on the retina of the myopic eye.
2. Hypermetropia (long-sightedness or far-sightedness): Hypermetropia is an eye defect because of which a person cannot see nearby objects clearly but can see faraway objects normally. By using spectacles with convex lenses, hypermetropia can be corrected, as a convex lens increases the converging power of the eye lens and therefore forms the images of nearby objects on the retina of the hypermetropic eye.
The two most common defects of vision (or defects of the eye) are the following.
1. Myopia (short-sightedness or near-sightedness): Myopia is an eye defect because of which a person cannot see faraway objects clearly but can see nearby objects normally. By using spectacles with concave lenses, myopia can be corrected, as a concave lens reduces the converging power of the eye lens and therefore forms the images of faraway objects on the retina of the myopic eye.
2. Hypermetropia (long-sightedness or far-sightedness): Hypermetropia is an eye defect because of which a person cannot see nearby objects clearly but can see faraway objects normally. By using spectacles with convex lenses, hypermetropia can be corrected, as a convex lens increases the converging power of the eye lens and therefore forms the images of nearby objects on the retina of the hypermetropic eye.v
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संबंधित प्रश्न
Which defect of vision can be rectified:
by using a convex lens?
What is the other name of old age hypermetropia?
What is short-sightedness? State the two causes of short-sightedness (or myopia). With the help of ray diagrams, show:
(i) the eye-defect short-sightedness.
(ii) correction of short-sightedness by using a lens.
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.
An eye has a far point of 2 m. What type of lens in spectacles would be needed to increase the far point to infinity? Also calculate the power of lens required. Is this eye long-sighted or short-sighted?
A young man has to hold a book at arm's length to be able to read it clearly. The defect of vision is:
(a) astigmatism
(b) myopia
(c) presbyopia
(d) hypermetropia
The defect of vision in which the eye-lens of a person gets progressively cloudy resulting in blurred vision is called:
(a) myopia
(b) presbyopia
(c) colourblindness
(d) cataract
When do we consider a student sitting in the class to be myopic? List two causes of this defect. Explain using a ray diagram how this defect of eye can be corrected.
Distinguish between the following pair of words:
Myopia and hypermetropia
Given below is a diagram depicting a defect of the human eye? Study the same and answer the question that follow:
Name the parts labeled 1 to 4.
Given below is a diagram depicting a defect of the human eye? Study the same and answer the question that follow:
Draw a labeled diagram to show how the above mentioned defect is rectified using the lens named above.
Give Reason:
Older people require glasses to read and write.
Explain the Term: Astigmatism
Give Technical Term:
The path which responsible for protecting the eye from sweat.
With respect to human eye explain:
(i) How is the image formed on the retina?
(ii) How is the amount of light entering the eye-controlled?
(iii) What type of lens is used for the correction of ‘Long sight’ defect?
(iv) With the help of a ray, diagram show the defect of the eye and then its correction after the use of a lens.
Mention, if the following statement is True or False
Hypermetropia is a defect of the eye caused due to the eyeball elongation
Nearsightedness : concave lens : : farsightedness : _______
Assertion: Myopia is the defect of vision in which a person cannot see distant objects clearly.
Reason: This due to eye-ball being too short.
Match the following:
| Column - I | Column - II |
| 1. Retina | a. Path way of light |
| 2. Pupil | b. Far point comes closer |
| 3. Ciliary muscles | c. near point moves away |
| 4. Myopia | d. Screen of the eye |
| 5. Hypermetropia | e. Power of accommodation |
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.
