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प्रश्न
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 an old man
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उत्तर
If the person is an old man, then the defect of vision is presbyopia. It usually occurs in old age when a person cannot see nearby objects clearly because of the loss of the eye's power of accommodation.
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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.
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.
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?
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.
What type of lenses-converging or diverging-would an optician prescribe for her?
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?
Differentiate between myopia and hypermetropia. What type of spectacles should be worn by a person having the defects of myopia as well as hypermetropia? How does it help?
Name the defect of vision which can be corrected by a diverging lens. Show clearly by a ray diagram how the lens corrects the defect.
A short-sighted person has a near point of 15 cm and a far point of 40 cm.
(a) Can he see clearly an object at a distance of:
(i) 5 cm?
(ii) 25 cm?
(iii) 50 cm?
(b) To see clearly an object at infinity, what kind of spectacle lenses does he need?
To read a book held at a distance of 25 cm, will she need converging or diverging spectacle lenses?
Explain the terms ‘adaptation’ and ‘accommodation’ with reference to the eye.
Enumerate the common defects of vision, their causes and the possible methods of correcting them.
Given below is a diagram depicting a defect of the human eye? Study the same and answer the question that follow:
Draw a labeled diagram to show how the above mentioned defect is rectified using the lens named above.
Give Technical Term:
The path which responsible for protecting the eye from sweat.
Choose the Odd One Out:
Observe the given below the figure, correct it and explain and write about the concept depicted in this figure.
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.
State reasons for Myopia. With the help of ray diagrams, show the:
- image formation by a myopic eye, and
- correction of myopia using an appropriate lens.
