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प्रश्न
Name an old age eye defect. What happens in it?
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उत्तर
Presbyopia is an age-old eye defect. In this condition, the lens loses flexibility resulting in far-sightedness.
Cataract is also very common in old people, the cornea becomes opaque and the vision is cut down even to blindness.
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.
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?
What is short-sightedness? State the two causes of short-sightedness (or myopia). With the help of ray diagrams, show:
(i) the eye-defect short-sightedness.
(ii) correction of short-sightedness by using a lens.
To read a book held at a distance of 25 cm, will she need converging or diverging spectacle lenses?
Differentiate between members of the following pair with reference to what is asked in the bracket.
Rods and cones (sensitivity).
Give Reason:
When you enter into a dark room from bright because of sunlight, you can not see things for a few seconds.
What type of lens is used to correct Astigmatism?
The diagram given below represents the cross-section of the human eye:
(i) Name the parts labeled 1—12.
(ii) What is the function of the part marked ‘10’?
(iii) What would happen if part ‘5’ is damaged or cut?
When do we consider a person to be myopic or hypermetropic? Explain using diagrams how the defects associated with myopic and hypermetropic eye can be corrected?
Observe the figure and answer the following questions:
- Name the defect of vision represented in the above figure.
- State the reasons for this defect.
- How is it corrected?
- Draw the diagram to show the correction of this defect.
