Advertisements
Advertisements
Question
List two causes of presbyopia. Draw labelled diagram of a lens used for the correction of this defect of vision.
Solution
Causes of presbyopia :
Aging
Weakening of ciliary muscles
It is treated by using a bifocal lens both concave and convex.
APPEARS IN
RELATED QUESTIONS
Given below is a diagram showing a defect of human eye. Study it and answer the following questions.
(i) Name the defect shown in the figure.
(ii) Give reason for this defect of eye in human being.
(iii) Name the type of lens used to correct the eye defect.
A student is unable to see clearly the words written on the blackboard placed at a distance of approximately 4 m from him. Name the defect of vision the boy is suffering from. Explain the method of correcting this defect.
Draw ray diagram for the:-
(i) defect of vision and also
(ii) for its correction.
A student sitting in the last row of the class-room is not able to read clearly the writing on the blackboard.
How can this defect by corrected?
What are the two most common defects of vision (or defects of eye)? How are they corrected?
What is short-sightedness? State the two causes of short-sightedness (or myopia). With the help of ray diagrams, show:
(i) the eye-defect short-sightedness.
(ii) correction of short-sightedness by using a lens.
A person having short-sight cannot see objects clearly beyond a distance of 1.5 m. What would be the nature and power of the corrective lens to restore proper vision?
An eye has a far point of 2 m. What type of lens in spectacles would be needed to increase the far point to infinity? Also calculate the power of lens required. Is this eye long-sighted or short-sighted?
Differentiate between members of the following pair with reference to what is asked in the bracket.
Rods and cones (sensitivity).
The diagram alongside represents a section of a mammalian eye.
(i) Label the parts 1 to 5 of the diagram.
(ii) State the function of the parts labelled 4 and 5.
(iii) With the help of a diagram show the short sightedness.
Nearsightedness : concave lens : : farsightedness : _______
