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प्रश्न
Observe the figure whether it is correct or not and explain the phenomenon.
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उत्तर
The figure shows a myopic eye, in which the eye lens is unable to focus the light rays coming from distant objects into the retina. In this defect, the image of a distant object is formed before the retina i.e., the light rays converge before the retina. Hence, to correct the defect a diverging lens (concave lens) of proper focal length is used, so that after refraction rays reach to retina and the person can see the image clearly.
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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?
Which defect of vision can be rectified:
by using a concave lens?
What is the other name for
hypermetropia
Name any two defects of vision which can be corrected by using spectacles.
A student sitting in the last row of the class-room is not able to read clearly the writing on the blackboard.
- Name the type of defect he is suffering from.
- How can this defect by corrected?
A student sitting in the last row of the class-room is not able to read clearly the writing on the blackboard.
How can this defect by corrected?
A person having short-sight cannot see objects clearly beyond a distance of 1.5 m. What would be the nature and power of the corrective lens to restore proper vision?
A person cannot see the distant objects clearly (though he can see the nearby objects clearly). He is suffering from the defect of vision called:
(a) cataract
(b) hypermetropia
(c) myopia
(d) presbyopia
A short-sighted person has a near point of 15 cm and a far point of 40 cm.
(a) Can he see clearly an object at a distance of:
(i) 5 cm?
(ii) 25 cm?
(iii) 50 cm?
(b) To see clearly an object at infinity, what kind of spectacle lenses does he need?
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 a young man
Differentiate between members of the following pair with reference to what is asked in bracket.
Myopia and hyperopia (cause of the defect)
Name an old age eye defect. What happens in it?
What is meant by optical illusion? Give one example.
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.
Choose the odd one out from the following terms and name the category to which the others belong.
Endolymph, Tympanic membrane, Semi-circular canal, Blind spot
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.
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.
Given below is a diagram depicting a defect of the human eye? Study the same and answer the question that follow:
Draw a labeled diagram to show how the above mentioned defect is rectified using the lens named above.
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?
The near point of the eye of a person is 50 cm. Find the nature and power of the corrective lens required by the person to enable him to see clearly the objects placed at 25 cm from the eye?
In what two whys is a yellow spot different from the blind spot?
Name an old age eye defect. Why is it caused?
Differentiate between:
Short-sightedness and Long-sightedness.
Differentiate between:
Myopia and Hypermetropia.
Explain the Term: Astigmatism
Explain the Term: Cataract
Give Technical Term:
The path which responsible for protecting the eye from sweat.
What type of lens is used to correct Astigmatism?
The diagram given below represents the cross-section of the human eye:
(i) Name the parts labeled 1—12.
(ii) What is the function of the part marked ‘10’?
(iii) What would happen if part ‘5’ is damaged or cut?
Given below is a diagrammatic representation of a defect of the human eye:
(i) Identify the defect.
(ii) Mention two reasons for the above defect.
(iii) State how the defect can be rectified.
(iv) Name the part of the eye responsible for maintaining the shape of the eyeball.
Myopia and hypermetropia can be corrected by:
Which of the following statement is correct?
Correlate the given sequence:
Hypermetropia : Convex lens : ______ : Concave lens
State reasons for Myopia. With the help of ray diagrams, show the:
- image formation by a myopic eye, and
- correction of myopia using an appropriate lens.
