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प्रश्न
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.
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उत्तर
Short-sightedness, or near-sightedness, is an eye defect because of which a person cannot see distant objects clearly but has normal near vision. Short-sightedness occurs because of the high converging power of the eye lens (images are formed in front of the retina) and because the eyeball is too long (images are formed in front of the retina).
(i) and (ii) The following diagram illustrates short-sightedness and how concave lenses can correct the defect by diverging the light rays entering the eye to form clear images of distant objects on the retina.
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संबंधित प्रश्न
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?
What is the scientific name of
short-sightedness
Name the defect of vision in which the eye-lens loses its power of accommodation due to old age.
Your friend can read a book perfectly well but cannot read the writing on blackboard unless she sits on the front row in class.
What type of lenses-converging or diverging-would an optician prescribe for her?
The near-point of a person suffering from hypermetropia is at 50 cm from his eye. What is the nature and power of the lens needed to correct this defect? (Assume that the near-point of the normal eye is 25 cm).
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?
Name the following:
The photosensitive pigment present in the rods of the retina.
Differentiate between members of the following pair with reference to what is asked in bracket.
Myopia and hyperopia (cause of the defect)
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.
Choose the correct answer :
Presbyopia is a disease of _____________
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 type of lens used to correct this eye defect.
Name the common defects of the eye.
Explain the Term: Hypermetropia
Assertion: Myopia is the defect of vision in which a person cannot see distant objects clearly.
Reason: This due to eye-ball being too short.
Draw ray diagram showing myopic eye.
Correlate the given sequence:
Hypermetropia : Convex lens : ______ : Concave lens
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.
