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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
Write the importance of ciliary muscles in the human eye. Name the defect of vision that arises due to gradual weakening of the ciliary muscles. What types of lenses are required by the person suffering from this defect to see the objects clearly?
Akshay, sitting in the last row in his class, could not see clearly the words write on the blackboard. When the teacher noticed it, he announced if any student sitting in the front row could volunteer to exchange his seat with Akshay. Salman immediately agreed to exchange his seat with Akshay. He could now see the words written on the blackboard clearly. The teacher thought it fit to send the message to Akshay’s parents advising them to get his eyesight checked.
In the context of the above event, answer the following questions:-
(a) Which defect of vision is Akshay suffering from? Which type of lens is used to correct this defect?
(b) State the values displayed by the teacher and Salman.
(c) In your opinion, in what way can Akshay express his gratitude towards the teacher and Salman?
Name the defect of vision in a person:
whose far point is less than infinity
Name the defect of vision in which the eye-lens loses its power of accommodation due to old age.
What is the far point of a person suffering from myopia (or short-sightedness)?
Your friend can read a book perfectly well but cannot read the writing on blackboard unless she sits on the front row in class.
Is she short-sighted or long-sighted?
The defect of vision which cannot be corrected by using spectacles is:
(a) myopia
(b) presbyopia
(c) cataract
(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
A short-sighted person has a near point of 15 cm and a far point of 40 cm.
(a) Can he see clearly an object at a distance of:
(i) 5 cm?
(ii) 25 cm?
(iii) 50 cm?
(b) To see clearly an object at infinity, what kind of spectacle lenses does he need?
Explain the terms ‘adaptation’ and ‘accommodation’ with reference to the eye.
Given below is a diagram depicting a defect of the human eye. Study the same and answer the question that follow:
Name the defect shown in the diagram.
Have a look at the posture of this girl who is reading a book and answer the questions which follow:
Name the problem she is facing.
State one role of ciliary muscles in the human eye.
A student has difficulty reading the blackboard while sitting in the last row. What could be the defect the child is suffering from? How can it be corrected?
State the main functions of the following:
Tears
Choose the correct answer :
Presbyopia is a disease of _____________
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.
Write scientific reason.
Nearsightedness, this defect can be corrected by using spectacles with concave lens.
Observe the given below the figure, correct it and explain and write about the concept depicted in this figure.
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.
Myopia may arise due to ____________.
