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प्रश्न
Name the following:
The photosensitive pigment present in the rods of the retina.
उत्तर
Rhodopsin
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संबंधित प्रश्न
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?
What is the far point and near point of the human eye with normal vision?
A student suffering from myopia is not able to see distinctly the objects placed beyond 5 m. List two possible reasons due to which this defect of vision may have arisen. With the help of ray diagrams, explain
(i) why the student is unable to see distinctly the objects placed beyond 5 m from his eyes.
(ii) the type of the corrective lens used to restore proper vision and how this defect is corrected by the use of this lens.
(b) If, in this case, the numerical value of the focal length of the corrective lens is 5 m, find the power of the lens as per the new Cartesian sign convention
the biological/technical terms for the lens of eye losing flexibility resulting in a kind of long-sightedness in middle aged people.
Which defect of vision can be rectified:
by using a concave lens?
Name any two defects of vision which can be corrected by using spectacles.
What is the far point of a person suffering from myopia (or short-sightedness)?
Name the defect of vision which can be corrected by a converging lens. Show clearly by a ray diagram how the lens corrects the defect.
What is long-sightedness? State the two causes of long-sightedness (or hypermetropia). With the help of ray diagrams, show:
(i) the eye-defect long-sightedness.
(ii) correction of long-sightedness by using a lens.
The defect of vision in which the eye-lens of a person gets progressively cloudy resulting in blurred vision is called:
(a) myopia
(b) presbyopia
(c) colourblindness
(d) cataract
By closing the eyes and gently pressing them by your palms, you may see some specks of brilliant light. How do you get this sensation while there is no light entering your eyes?
Name an old age eye defect. Why is it caused?
Draw a neat labeled diagram to show how hypermetropia can be rectified.
Explain the Term: Astigmatism
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.
In Myopia the human eye _______.
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?
Correlate the given sequence:
Hypermetropia : Convex lens : ______ : Concave lens
Observe the following diagram and answer questions following it:
- Identify the defect of vision shown.
- List its two causes.
- Name the type of lens used for the correction of this defect.
