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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
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.
List three common refractive defects of vision. Suggest the way of correcting these defects.
Name the defect of vision in a person:
whose near point is more than 25 on away.
Which defect of vision can be rectified:
by using a concave lens?
What is the other name of old age hypermetropia?
Name the body part with which the terms myopia and hypermetropia are connected.
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.
A person suffering from the eye-defect myopia (short-sightedness) can see clearly only up to a distance of 2 metres. What is the nature and power of lens required to rectify this 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.
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.
Observer the following diagram and answer the questions.
a) Which eye defect is shown in this diagram?
b) What are the possible reasons for this eye defect?
c) How this defect is corrected, write it in brief?
When do we consider a student sitting in the class to be myopic? List two causes of this defect. Explain using a ray diagram how this defect of eye can be corrected.
Select the odd one in the following series:
Endolymph, Tympanic membrane, Semi-circular canal, Blind spot.
Have a look at the posture of this woman who is reading a book and answer the questions which follow:
What kind of looking glasses she needs?
Anuja cannot see the blackboard writing but she can see nearby things.
(a) What is the eye defect she is suffering from?
(b) State the possible reason for her defect.
(c) How is it corrected
Name an old age eye defect. Why is it caused?
Explain the Term: Cataract
Choose the Odd One Out:
Given below is a diagram showing a defect of vision. Name the defect of vision and draw an accurately labelled diagram to correct this defect.
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.
