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प्रश्न
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?
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उत्तर
a) Myopia or Nearsightedness
b) Possible reasons of defect
i. The curvature of the cornea and the eye lens increases. The muscles near the lens cannot relax so that the converging power of the lens remains large.
ii. The eyeball elongates so that the distance between the lens and the retina increases
c) correction of defect: this defect can be corrected using spectacles with concave lens. This lens diverges the incident rays and these diverged rays can be converged by the lens in the eye to form image on the retina.
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संबंधित प्रश्न
Given below is a diagram showing a defect of human eye. Study it and answer the following questions.
(i) Name the defect shown in the figure.
(ii) Give reason for this defect of eye in human being.
(iii) Name the type of lens used to correct the eye defect.
In a Std. X class out of 40 students 10 students use spectacles, 2 students have positive power and 8 students have negative power of lenses in their spectacles.
Answer the following questions:
(1) What does the negative power indicate?
(2) What does the positive power indicate?
(3) Generally which type of spectacles do most of the students use?
(4) What defect of eyesight do most of the students suffer from?
(5) Give two possible reasons for the above defect.
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?
About 45 lac people in the developing countries are suffering from corneal blindness. About 30 lac children below the age of 12 years suffering from this defect can be cured by replacing the defective cornea with the cornea of a donated eye. How and why can students of your age involve themselves to create awareness about this fact among people?
Which defect of vision can be rectified:
by using a concave lens?
What is the other name for
hypermetropia
What is the far point of a person suffering from myopia (or short-sightedness)?
Though a woman can see the distant object clearly, she cannot see the nearby objects clearly. She is suffering from the defect of vision called:
(a) long-sight
(b) short-sight
(c) hind-sight
(d) mid-sight
The picture given here shows a person wearing 'half-moon' spectacles. What sort of eye-defect do do you think he has? Why are these particular spectacles useful to him?
To read a book held at a distance of 25 cm, will she need converging or diverging spectacle lenses?
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
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 a young man
Describe the mechanism of focusing the image of a distant object in your eye when you raise your head after reading a book.
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.
A student cannot see a chart hanging on a wall placed at a distance of 3 m from him. Name the defect of vision he is suffering from. How can it be corrected? Draw ray diagrams for the (i) defect of vision and also (ii) for 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.
List two causes of presbyopia. Draw labelled diagram of a lens used for the correction of this defect of vision.
Given below is a diagram depicting a defect of the human eye? Study the same and answer the question that follow:
Give two possible reasons for this defect of the eye in human beings.
Given below is a diagram depicting a defect of the human eye? Study the same and answer the question that follow:
Name the parts labeled 1 to 4.
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.
Rewrite the following table so as to match second and third column with first column.
|
Column I
|
Column II
|
Column III
|
|
(i) Myopia
|
Old age problem
|
Bifocal lens
|
|
(ii) Presbyopia
|
Nearsightedness
|
Concave lens.
|
Name an old age eye defect. Why is it caused?
Give Reason:
When you enter into a dark room from bright because of sunlight, you can not see things for a few seconds.
Differentiate between:
Short-sightedness and Long-sightedness.
Differentiate between:
Myopia and Hypermetropia.
Draw a neat labeled diagram to show how hypermetropia can be rectified.
Explain the Term: Hypermetropia
Name the following:
The defect of the human eye caused due to the uneven surface of the cornea.
Give Technical Term:
The type of lens used to correct myopia is
Study the following diagram carefully and then answer the questions that follow. The diagram is depicting a defect of the human eye :
(i) Identify the defect shown in the diagram.
(ii) Give two possible reasons for the above defect.
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.
What are the causes of ‘Myopia’?
A person cannot see distinctly objects kept beyond 2 m. This defect can be corrected by using a lens of power:
Myopia may arise due to ____________.
Which of the following statement is correct?
A person is unable to see clearly a poster fixed on a distant wall. He however sees it clearly when standing at a distance of about 2 m from the wall.
- Draw ray diagram to show the formation of image by his eye lens when he is far away from the wall.
- List two possible reasons of this defect of vision.
- Draw ray diagram to show the correction of this defect using appropriate lens.
