Advertisements
Advertisements
Question
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.
Advertisements
Solution
Myopia is a visual impairment in which a person can see all around objects clearly, but finds it difficult to comfortably focus on a single object. This eye is referred to as the myopia eye.
Myopia can be caused by:
- increase in curvature of the lens.
- increase in the length of the eye ball.
(a) A myopic eye's far point is close to that infinite distance. In front of the retina, it creates the separate object image depicted in the figure.
(b) Concave lens has an ability to diverge incoming rays, it is used to correct this defect of vision. The image is allowed to form at the retina by using a concave lens of suitable power as shown in the figure.
APPEARS IN
RELATED QUESTIONS
What is the scientific name of
short-sightedness
Name any two defects of vision which can be corrected by using spectacles.
A young man has to hold a book at arm's length to be able to read it clearly. The defect of vision is:
(a) astigmatism
(b) myopia
(c) presbyopia
(d) hypermetropia
To read a book held at a distance of 25 cm, will she need converging or diverging spectacle lenses?
Differentiate between members of the following pair with reference to what is asked in bracket.
Myopia and hyperopia (cause of the defect)
Name the following:
The photosensitive pigment present in the rod cells of the retina.
Choose the correct answer :
Presbyopia is a disease of _____________
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.
|
Solve the following question:
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?
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.
- What are the two conditions shown in sections A and B of the eye as applicable to her.
- What kind of reading glasses does she need?
 |
 |
| A | B |
