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प्रश्न
Name the defect of vision which can be corrected by a diverging lens. Show clearly by a ray diagram how the lens corrects the defect.
उत्तर
Myopia (short-sightedness) is a defect of vision that can be corrected by using diverging or concave lenses. The following ray diagram clearly shows the correction of myopia by using a diverging lens.
A person with myopia does not see distant objects clearly but has normal near vision. Fig. (a) shows the far point of the myopic eye, and fig. (b) shows the parallel light rays from a distant object forming an image at a point in front of the retina. To correct this defect, a concave lens is used, because of which, in fig. (c), we observe the rays being diverged first so that they form a clear image on the retina.
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संबंधित प्रश्न
What is the far point and near point of the human eye with normal vision?
Name one defect of vision (or eye) which cannot be corrected by any type of spectacle lenses.
A young man has to hold a book at arm's length to be able to read it clearly. The defect of vision is:
(a) astigmatism
(b) myopia
(c) presbyopia
(d) hypermetropia
A person cannot read newspaper placed nearer than 50 cm from his eyes. Name the defect of vision he is suffering from. Draw a ray diagram to illustrate this defect. List its two possible causes. Draw a ray diagram to show how this defect may be corrected using a lens of appropriate focal length.
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.
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.
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.
Rewrite the following table so as to match second and third column with first column.
|
Column I
|
Column II
|
Column III
|
|
(i) Myopia
|
Old age problem
|
Bifocal lens
|
|
(ii) Presbyopia
|
Nearsightedness
|
Concave lens.
|
What type of lens is used to correct Astigmatism?
Nearsightedness: elongated eyeball : : farsightedness: _______
