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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?
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उत्तर १
Ciliary muscles adjust the shape of the eye lens in order to focus the light properly for objects at different distances.
Presbyopia is the defect that arises due to gradual weakening of ciliary muscles in old age. It is corrected by using convex lenses.
(a) Akshay is suffering from myopia (nearsightedness). Concave lenses are used to correct myopia.
(b) Salman is a helpful classmate of Akshay and the teacher is caring and concerned about the studies of Akshay.
(c) Akshay can express his gratitude towards Salman and the teacher by going to the doctor to get his eyesight checked.
उत्तर २
The curvature of the eye lens can be adjusted by the ciliary muscles. This changes the focal length of the lens. The defect which arises because of the gradual weakening of the ciliary muscles is known as presbyopia. A bifocal lens can be used to correct presbyopia.
Answers to the context questions:-
(a) Akshay is not able to see from a far distance, so he is suffering from myopia or nearsightedness. A concave lens should be used to correct this defect.
(b) The teacher displayed presence of mind and pro-activeness, and she is of a considerate nature. Salman displayed the virtue of friendship and is caring in nature.
(c) Akshay should thank the teacher and Salman in front of the entire class.
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संबंधित प्रश्न
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 far point of a myopic person is 80 cm in front of the eye. What is the nature and power of the lens required to correct the problem?
By closing the eyes and gently pressing them by your palms, you may see some specks of brilliant light. How do you get this sensation while there is no light entering your eyes?
A person is unable to read a book placed closer than 1 meter from his eyes. Identify the defect of vision in his eyes. Draw the ray diagrams to show the defect of vision and its correction.
An old man cannot see objects closer than 1 m from the eye clearly. Name the defect of vision he is suffering from. How can it be corrected? Draw ray diagram for the (i) defect of vision and also (ii) for its correction.
Observer the following diagram and answer the questions.
a) Which eye defect is shown in this diagram?
b) What are the possible reasons for this eye defect?
c) How this defect is corrected, write it in brief?
Explain the Term: Astigmatism
Due to elongation of _______ and increase in curvature of the eye lens, a person cannot see distant objects clearly.
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.
Correlate the given sequence:
Hypermetropia : Convex lens : ______ : Concave lens
