Advertisements
Advertisements
Question
Explain with the help of labelled ray-diagram, the defect of vision called hypermetropia, and hot it is corrected by a lens.
Solution
Hypermetropia is a defect of vision because of which a person cannot see nearby objects clearly but has normal distant vision. Hypermetropia occurs because the converging power of the eye lens is low and the images of nearby objects are formed behind the retina. As a result, the person cannot see these objects clearly. In certain other cases, hypermetropia is caused because the eye ball is too short. This, too, causes the formation of images behind the retina, as the retina is at a smaller distance from the eye lens. The near point of a hypermetropic eye is located more than 25 centimetres from the eye. The following ray diagram explains the hypermetropic eye and how the defect is corrected by using convex lenses. A convex lens is a converging lens that converges light rays and forms virtual images of nearby objects at the eye's near point. The eye lens then easily focusses the light rays from the near point and forms clear images of the objects on the retina.
APPEARS IN
RELATED QUESTIONS
List three common refractive defects of vision. Suggest the way of correcting these defects.
the biological/technical terms for the lens of eye losing flexibility resulting in a kind of long-sightedness in middle aged people.
Name one defect of vision (or eye) which cannot be corrected by any type of spectacle lenses.
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
Draw a ray diagram to show how Hypermetropia is defect can be corrected using a lens.
In what two whys is a yellow spot different from the blind spot?
Differentiate between:
Myopia and Hypermetropia.
Given below is a diagram showing a defect of vision. Name the defect of vision and draw an accurately labelled diagram to correct this defect.
When do we consider a person to be myopic or hypermetropic? Explain using diagrams how the defects associated with myopic and hypermetropic eye can be corrected?
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 |
