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प्रश्न
Explain the Term: Presbyopia
उत्तर
Presbyopia: It is a condition affecting older people who cannot see near objects clearly. Their lens loses flexibility resulting in a kind of far-sightedness. This again is corrected by a convex lens.
APPEARS IN
संबंधित प्रश्न
In a Std. X class out of 40 students 10 students use spectacles, 2 students have positive power and 8 students have negative power of lenses in their spectacles.
Answer the following questions:
(1) What does the negative power indicate?
(2) What does the positive power indicate?
(3) Generally which type of spectacles do most of the students use?
(4) What defect of eyesight do most of the students suffer from?
(5) Give two possible reasons for the above defect.
What is the far point and near point of the human eye with normal vision?
Name the defect of vision in which the eye-lens loses its power of accommodation due to old age.
What is the other name of old age hypermetropia?
Your friend can read a book perfectly well but cannot read the writing on blackboard unless she sits on the front row in class.
Is she short-sighted or long-sighted?
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?
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 bracket.
Myopia and hyperopia (cause of the defect)
Differentiate between members of the following pair with reference to what is asked in the bracket.
Rods and cones (sensitivity).
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 is Hypermetropia (far sightedness)?
Select the odd one in the following series:
Endolymph, Tympanic membrane, Semi-circular canal, Blind spot.
Write whether the following is true or false:
A convex lens is used for correcting myopia.
Choose the correct answer :
Presbyopia is a disease of _____________
Draw a neat labeled diagram to show how hypermetropia can be rectified.
What type of lens is used to correct Astigmatism?
Due to elongation of _______ and increase in curvature of the eye lens, a person cannot see distant objects clearly.
Correlate the given sequence:
Hypermetropia : Convex lens : ______ : Concave lens
Name the following:
Two kinds of accomodations.
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.
