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Question
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?
Solution 1
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.
Solution 2
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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RELATED QUESTIONS
Millions of people in the developing countries of the world are suffering from corneal blindness. These persons can be cured by replacing the defective cornea with the cornea of a donated eye. A charitable society of your city has organised a campaign in your neighbourhood in order to create awareness about this fact. If you are asked to participate in this mission, how would you contribute in this noble cause?
(i) State the objective of organising such campaigns.
(ii) List two arguments which you would give to motivate the people to donate their eyes after death.
(iii) List two values which are developed in the persons who actively participate and contribute in such programmes.
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?
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The photosensitive pigment present in the rods of the retina.
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The type of lens used to correct myopia is
What type of lens is used to correct Astigmatism?
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Observe the following diagram and answer questions following it:
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