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प्रश्न
Enumerate the common defects of vision, their causes and the possible methods of correcting them.
उत्तर
| Defect of vision | Cause | Corrective measure |
| Myopia | Lengthening of eye ball from front to back or the lens is too curved. | Using suitable concave lens |
| Hyperopia | Shortening of eye ball from front to back or the lens is too flat. | Using suitable convex lens |
| Astigmatism | Uneven curvature of the cornea | Using suitable cylindrical lenses |
| Presbyopia | Loss of flexibility of lens | Using suitable convex lens |
| Cataract | Lens turning opaque | Surgery or use of convex lens or implantation of plastic lens. |
| Colour blindness | Genetic defect | No control measure |
| Squint | Formation of cross-eye | Surgery and suitable exercise |
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संबंधित प्रश्न
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.
Name the defect of vision in which the eye-lens loses its power of accommodation due to old age.
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
Name the following:
The photosensitive pigment present in the rods of the retina.
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.
Select the odd one in the following series:
Endolymph, Tympanic membrane, Semi-circular canal, Blind spot.
Given alongside is a diagram depicting a defect of the human eye. Study the same and then answer the questions that follow:
(i) Identify the defect.
(ii) Name the parts labelled 1, 2 and 3.
(iii) Give labelled two possible reasons for this eye defect.
(iv) Draw a labelled diagram to show how the above mentioned defect is rectified.
The diagram alongside represents a section of a mammalian eye.
(i) Label the parts 1 to 5 of the diagram.
(ii) State the function of the parts labelled 4 and 5.
(iii) With the help of a diagram show the short sightedness.
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.
Have a look at the posture of this woman who is reading a book and answer the questions which follow:
What are the two conditions shown in sections A and B of the eye as applicable to her?
Give Reason:
Deficiency of vitamin A causes night blindness.
Explain the Term: Hypermetropia
Explain the Term: Presbyopia
Give Technical Term:
The type of lens used to correct myopia is
Complete the following sentence with appropriate word :
An inability to focus on nearby objects due to loss of elasticity of the lens with age is called Iris.
Nearsightedness: elongated eyeball : : farsightedness: _______
What are the causes of ‘Myopia’?
A person needs a lens of power –4.5 D for correction of her vision.
- What kind of defect in vision is she suffering from?
- What is the focal length of the corrective lens?
- What is the nature of the corrective lens?
