Advertisements
Advertisements
Question
List three common refractive defects of vision. Suggest the way of correcting these defects.
Solution
The three common refractive defects of vision are as follows:-
Myopia (short-sightedness):- It is corrected by using spectacles having concave lenses of appropriate power.
Hypermetropia (far-sightedness):- It is corrected by using spectacles having convex lenses of appropriate power.
Presbyopia:- This defect is corrected using bifocal lenses of appropriate power in which the upper part consists of a concave lens (to correct myopia) and the lower part consists of a convex lens (to correct hypermetropia).
APPEARS IN
RELATED QUESTIONS
the biological/technical terms for the lens of eye losing flexibility resulting in a kind of long-sightedness in middle aged people.
Name the defect of vision which can be corrected by a converging lens. Show clearly by a ray diagram how the lens corrects the defect.
What is Hypermetropia (far sightedness)?
State the main functions of the following:
Tears
A person is unable to see objects distinctly placed within 50 cm from his eyes.
(a) Name the defect of vision the person is suffering from and list its two possible causes.
(b) Draw a ray diagram to show the defect in the above case.
(c) Mention the type of lens used by him for the correction of the defect and calculate its power. Assume that the near point for the normal eye is 25 cm.
(d) Draw a labeled diagram for the correction of the defect in the above case.
Draw a neat labeled diagram to show how hypermetropia can be rectified.
Name the following:
The defect of the human eye caused due to the uneven surface of the cornea.
Nearsightedness: elongated eyeball : : farsightedness: _______
Observe the figure whether it is correct or not and explain the phenomenon.
Observe the following diagram and answer questions following it:
- Identify the defect of vision shown.
- List its two causes.
- Name the type of lens used for the correction of this defect.
