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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?
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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
What is myopia?
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?
What are the two most common defects of vision (or defects of eye)? How are they corrected?
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
Explain the terms ‘adaptation’ and ‘accommodation’ with reference to the eye.
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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.
A person cannot read newspaper placed nearer than 50 cm from his eyes. Name the defect of vision he is suffering from. Draw a ray diagram to illustrate this defect. List its two possible causes. Draw a ray diagram to show how this defect may be corrected using a lens of appropriate focal length.
What is Hypermetropia (far sightedness)?
Choose the correct answer :
Presbyopia is a disease of _____________
Give Reason:
Why do we see clearly in the central region of the retina?
Differentiate between:
Myopia and Hypermetropia.
Explain the Term: Cataract
What type of lens is used to correct Hypermetropia?
Mention, if the following statement is True or False
Hypermetropia is a defect of the eye caused due to the eyeball elongation
Choose the Odd One Out:
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.
Correlate the given sequence:
Hypermetropia : Convex lens : ______ : Concave lens
A teacher drew the diagram of the heart on the blackboard and told the students to copy it in their notebooks. Mahesh couldn't see the diagram clearly as it appeared blurred to him.
- Name the defect of the eye Mahesh is suffering from.
- Where is the image formed in this defect?
- Mahesh consults an eye doctor and is prescribed suitable lenses to correct the defect. Which type of lens do his spectacles have?
