Advertisements
Advertisements
प्रश्न
Explain the Term: Cataract
Advertisements
उत्तर
Cataract: It is a condition in which the lens turns opaque and the vision is cut down even to total blindness. It can be corrected by surgically removing the lens and by using spectacles with highly convex lense.
संबंधित प्रश्न
Your friend can read a book perfectly well but cannot read the writing on blackboard unless she sits on the front row in class.
- Is she short-sighted or long-sighted?
- What type of lenses-converging or diverging-would an optician prescribe for her?
A man can read the number of a distant bus clearly but he finds difficulty in reading a book.
- From which defect of the eye is he suffering?
- What type of spectacle lens should he use to correct the defect?
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.
Name the following:
The photosensitive pigment present in the rods of the retina.
An old man cannot see objects closer than 1 m from the eye clearly. Name the defect of vision he is suffering from. How can it be corrected? Draw ray diagram for the (i) defect of vision and also (ii) for its correction.
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.
|
Draw a neat labeled diagram to show how hypermetropia can be rectified.
Explain the Term: Astigmatism
Nearsightedness : concave lens : : farsightedness : _______
Differentiate the eye defects: Myopia and Hypermetropia
