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प्रश्न
Give Reason:
Why do we see clearly in the central region of the retina?
उत्तर
The central region of the retina has fovea centralis, with the yellow spot area surrounding it. There are only cone cells responsible for clear vision and details of the objects.
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संबंधित प्रश्न
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.
What is the other name for
hypermetropia
What are the two most common defects of vision (or defects of eye)? How are they corrected?
The defect of vision which cannot be corrected by using spectacles is:
(a) myopia
(b) presbyopia
(c) cataract
(d) hypermetropia
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
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?
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
Name the following:
The photosensitive pigment present in the rods of the retina.
Name an old age eye defect. What happens in it?
List two causes of presbyopia. Draw labelled diagram of a lens used for the correction of this defect of vision.
Write whether the following is true or false:
A convex lens is used for correcting myopia.
A person is unable to see objects distinctly placed within 50 cm from his eyes.
(a) Name the defect of vision the person is suffering from and list its two possible causes.
(b) Draw a ray diagram to show the defect in the above case.
(c) Mention the type of lens used by him for the correction of the defect and calculate its power. Assume that the near point for the normal eye is 25 cm.
(d) Draw a labeled diagram for the correction of the defect in the above case.
Explain the Term: Cataract
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
What type of lens is used to correct Astigmatism?
What are the causes of ‘Myopia’?
Which of the following statement is correct?
Myopia may arise due to ____________.
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.
