Advertisements
Advertisements
Question
A person can read a book clearly only if he holds it at an arm's length from him. Name the defect of vision:
if the person is a young man
Advertisements
Solution
If the person is a young man, the defect of vision is hypermetropia. Hypermetropia occurs either because the eye lens has low converging power or because the eyeball is too short. This makes the near vision defective.
APPEARS IN
RELATED QUESTIONS
List three common refractive defects of vision. Suggest the way of correcting these defects.
The far point of a myopic person is 80 cm in front of the eye. What is the nature and power of the lens required to correct the problem?
A student suffering from myopia is not able to see distinctly the objects placed beyond 5 m. List two possible reasons due to which this defect of vision may have arisen. With the help of ray diagrams, explain
(i) why the student is unable to see distinctly the objects placed beyond 5 m from his eyes.
(ii) the type of the corrective lens used to restore proper vision and how this defect is corrected by the use of this lens.
(b) If, in this case, the numerical value of the focal length of the corrective lens is 5 m, find the power of the lens as per the new Cartesian sign convention
What is the scientific name of
long-sightedness?
Name the defect of vision in which the eye-lens loses its power of accommodation due to old age.
Name the body part with which the terms myopia and hypermetropia are connected.
What is the far point of a person suffering from myopia (or short-sightedness)?
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?
The defect of vision which cannot be corrected by using spectacles is:
(a) myopia
(b) presbyopia
(c) cataract
(d) hypermetropia
The near point of a long-sighted person is 50 cm from the eye.
(a) Can she see clearly an object at:
(i) a distance of 20 cm?
(ii) at infinity?
What is meant by optical illusion? Give one example.
What is Hypermetropia (far sightedness)?
Draw a ray diagram to show how Hypermetropia is defect can be corrected using a lens.
Distinguish between the following pair of words:
Myopia and hypermetropia
Choose the correct answer :
Presbyopia is a disease of _____________
Explain the Term: Astigmatism
The diagram given below represents the cross-section of the human eye:

(i) Name the parts labeled 1—12.
(ii) What is the function of the part marked ‘10’?
(iii) What would happen if part ‘5’ is damaged or cut?
Assertion: Concave mirrors are used as reflectors in torches, vehicle head lights and in search lights.
Reason: When an object is placed beyond the center of curvature of a concave mirror, the image formed is real and inverted.
A student sitting at the back of the classroom cannot read clearly the letters written on the blackboard. What advice will a doctor give to her? Draw ray diagram for the correction of this defect.
A teacher drew the diagram of the heart on the blackboard and told the students to copy it in their notebooks. Mahesh couldn't see the diagram clearly as it appeared blurred to him.
- Name the defect of the eye Mahesh is suffering from.
- Where is the image formed in this defect?
- Mahesh consults an eye doctor and is prescribed suitable lenses to correct the defect. Which type of lens do his spectacles have?
