Advertisements
Advertisements
प्रश्न
List two causes of presbyopia. Draw labelled diagram of a lens used for the correction of this defect of vision.
उत्तर
Causes of presbyopia :
Aging
Weakening of ciliary muscles
It is treated by using a bifocal lens both concave and convex.
APPEARS IN
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.
A student is unable to see clearly the words written on the blackboard placed at a distance of approximately 4 m from him. Name the defect of vision the boy is suffering from. Explain the method of correcting this defect.
Draw ray diagram for the:-
(i) defect of vision and also
(ii) for its correction.
Name the defect of vision in a person:
whose near point is more than 25 on away.
Where is the near point of a person suffering from hypermetropia (or long-sightedness)?
The near point of a long-sighted person is 50 cm from the eye.
(a) Can she see clearly an object at:
(i) a distance of 20 cm?
(ii) at infinity?
Describe the mechanism of focusing the image of a distant object in your eye when you raise your head after reading a book.
Name the following:
The photosensitive pigment present in the rod cells of the retina.
Give Reason:
Older people require glasses to read and write.
Explain the Term: Presbyopia
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.
