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प्रश्न
Explain two possible reasons of myopia. How can it be corrected? Explain with a suitable diagram.
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उत्तर
Possible reasons of myopia:-
(i) Ciliary muscles do not relax sufficiently. Therefore, the converging power of the eye lens becomes high.
(ii) The distance between the eye lens and the retina increases (relative to the normal eye) as the eyeball is lengthened (elongated) or the eye lens is curved.
Correcting myopia:-
(i) Myopia is corrected using a suitable concave lens. Light rays are diverged by the concave lens before they strike the eye lens.
(ii) A concave lens of appropriate power is chosen to produce the required divergence. Hence, after the converging action of the eye lens, the image is formed on the retina.
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संबंधित प्रश्न
What is myopia?
A person with a myopic eye cannot see objects beyond 1.2 m distinctly. What should be the type of the corrective lens used to restore proper vision?
the biological/technical terms for the lens of eye losing flexibility resulting in a kind of long-sightedness in middle aged people.
A student is unable to see clearly the words written on the black board placed at a distance of approximately 3 m from him. Name the defect of vision the boy is suffering from. State the possible causes of this defect and explain the method of correcting it.
Name the defect of vision which makes the eye-lens cloudy resulting in blurred vision.
What is the other name of old age hypermetropia?
Name any two defects of vision which can be corrected by using spectacles.
Name the body part with which the terms myopia and hypermetropia are connected.
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?
- What type of lenses-converging or diverging-would an optician prescribe for her?
Your friend can read a book perfectly well but cannot read the writing on blackboard unless she sits on the front row in class.
What type of lenses-converging or diverging-would an optician prescribe for her?
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 are the two most common defects of vision (or defects of eye)? How are they corrected?
Explain with the help of labelled ray diagram, the defect of vision called myopia and how it is corrected by a lens.
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.
A person cannot see the distant objects clearly (though he can see the nearby objects clearly). He is suffering from the defect of vision called:
(a) cataract
(b) hypermetropia
(c) myopia
(d) presbyopia
To read a book held at a distance of 25 cm, will she need converging or diverging spectacle lenses?
Which part of the eye is grafted in a needy patient from a donated eye?
Enumerate the common defects of vision, their causes and the possible methods of correcting them.
State the main functions of the following:
Tears
Write whether the following is true or false:
A convex lens is used for correcting myopia.
Given below is a diagram depicting a defect of the human eye? Study the same and answer the question that follow :
Name the type of lens used to correct this eye defect.
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.
Give Reason:
When you enter into a dark room from bright because of sunlight, you can not see things for a few seconds.
Name the following:
The defect of the human eye caused due to the uneven surface of the cornea.
Given below is a diagrammatic representation of a defect of the human eye:
(i) Identify the defect.
(ii) Mention two reasons for the above defect.
(iii) State how the defect can be rectified.
(iv) Name the part of the eye responsible for maintaining the shape of the eyeball.
Choose the Odd One Out:
Nearsightedness: elongated eyeball : : farsightedness: _______
Nearsightedness : concave lens : : farsightedness : _______
What are the causes of ‘Myopia’?
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.
Draw ray diagram showing myopic eye.
When do we consider a person to be myopic or hypermetropic? Explain using diagrams how the defects associated with myopic and hypermetropic eye can be corrected?
State reasons for Myopia. With the help of ray diagrams, show the:
- image formation by a myopic eye, and
- correction of myopia using an appropriate lens.
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 |
