Advertisements
Advertisements
Question
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.
Advertisements
Solution
(a) The defect of the vision is hypermetropia
Hypermetropia is caused due to:
(i) reduction in the curvature of the lens
(ii) a decrease in the size of the eyeball
(b) Ray diagram:
(c) The corrective lens used for this defect is a convex lens.
Given that the near point of the eye is at 50 cm. The convex lens should form the image of the object placed at the distance 25 cm on the near point of the defective eye.
v = −50 cm
u = −25 cm
`1/"f" = 1/"v"-1/"u"`
⇒ `1/"f"=1/((-50))-1/((-25))=1/50`
Power,`"P"=100/50=+2"D"`
(d) Ray diagram showing the correction of the defect:
APPEARS IN
RELATED QUESTIONS
What is the scientific name of
long-sightedness?
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
Describe the mechanism of focusing the image of a distant object in your eye when you raise your head after reading a book.
Explain the terms ‘adaptation’ and ‘accommodation’ with reference to the eye.
State one role of ciliary muscles in the human eye.
Observer the following diagram and answer the questions.
a) Which eye defect is shown in this diagram?
b) What are the possible reasons for this eye defect?
c) How this defect is corrected, write it in brief?
Explain the Term: Hypermetropia
What type of lens is used to correct Hypermetropia?
Assertion: Myopia is the defect of vision in which a person cannot see distant objects clearly.
Reason: This due to eye-ball being too short.
Given alongside is a diagram depicting a defect of the human eye. Study the same and answer the questions that follow:
 |
- Name the defect shown in the diagram.
- Give two possible reasons for this defect.
- Name the parts labelled 1 to 4.
- Name the type of lens used to correct this eye defect.
- Draw a labelled diagram to show how the above mentioned defect is rectified using the lens named above.
