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The kind of lens required to correct Myopia
A student is unable to see clearly the words written on the black board placed at a distance of approximately 3 m from him. Name the defect of vision the boy is suffering from. State the possible causes of this defect and explain the method of correcting it.
The near-point of a person suffering from hypermetropia is at 50 cm from his eye. What is the nature and power of the lens needed to correct this defect? (Assume that the near-point of the normal eye is 25 cm).
The defect of vision which cannot be corrected by using spectacles is:
(a) myopia
(b) presbyopia
(c) cataract
(d) hypermetropia
Name the following:
The photosensitive pigment present in the rod cells of the retina.
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
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Nearsightedness
|
Concave lens.
|
Differentiate between:
Short-sightedness and Long-sightedness.
Choose the Odd One Out:
Nearsightedness : concave lens : : farsightedness : _______
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.
