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प्रश्न
Due to elongation of _______ and increase in curvature of the eye lens, a person cannot see distant objects clearly.
विकल्प
eyeball
pupil
eyelid
cornea
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उत्तर
Due to elongation of eyeball and increase in curvature of the eye lens, a person cannot see distant objects clearly.
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संबंधित प्रश्न
Given below is a diagram showing a defect of human eye. Study it and answer the following questions.
(i) Name the defect shown in the figure.
(ii) Give reason for this defect of eye in human being.
(iii) Name the type of lens used to correct the eye defect.
Do you know that the corneal-impairment can be cured by replacing the defective cornea with the cornea of the donated eye? How and why should we organise groups to motivate the community members to donate their eyes after death?
List three common refractive defects of vision. Suggest the way of correcting these defects.
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?
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
Name the defect of vision in a person:
whose near point is more than 25 on away.
Name the defect of vision in a person:
whose far point is less than infinity
Which defect of vision can be rectified:
by using a convex lens?
Name the defect of vision in which the eye-lens loses its power of accommodation due to old age.
Name the defect of vision which makes the eye-lens cloudy resulting in blurred vision.
What is the other name of old age hypermetropia?
Name any two defects of vision which can be corrected by using spectacles.
Where is the near point of a person suffering from hypermetropia (or long-sightedness)?
A man can read the number of a distant but clearly but he finds difficulty in reading a book.
What type of spectacle lens should he use to correct the defect?
What are the two most common defects of vision (or defects of eye)? How are they corrected?
Differentiate between myopia and hypermetropia.
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?
An eye has a near point distance of 0.75 m. What sort of lens in spectacles would be needed to reduce the near point distance to 0.25 m? Also calculate the power of lens required. Is this eye long-sighted or short-sighted?
The defect of vision which cannot be corrected by using spectacles is:
(a) myopia
(b) presbyopia
(c) cataract
(d) hypermetropia
The picture given here shows a person wearing ‘half-moon’ spectacles. What sort of eye-defect do you think he has? Why are these particular spectacles useful to him?
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?
Which part of the eye is grafted in a needy patient from a donated eye?
Name the following:
The photosensitive pigment present in the rods of the retina.
Name the following:
The eye defect caused due to shortening of the eye ball from front to back.
Name an old age eye defect. What happens in it?
Explain the terms ‘adaptation’ and ‘accommodation’ with reference to the eye.
Have a look at the posture of this girl who is reading a book and answer the questions which follow:
Name the problem she is facing.
A person is unable to read a book placed closer than 1 meter from his eyes. Identify the defect of vision in his eyes. Draw the ray diagrams to show the defect of vision and its correction.
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.
Draw a ray diagram to show how Hypermetropia is defect can be corrected using a lens.
List two causes of presbyopia. Draw labelled diagram of a lens used for the correction of this defect of vision.
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
Write whether the following is true or false:
A convex lens is used for correcting myopia.
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.
Have a look at the posture of this woman who is reading a book and answer the questions which follow:
What are the two conditions shown in sections A and B of the eye as applicable to her?
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?
Give Technical Term:
The type of lens used to correct myopia is
Nearsightedness : concave lens : : farsightedness : _______
Observe the figure whether it is correct or not and explain the phenomenon.
